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PLANT, PROPERTY AND EQUIPMENT

EQUITY INVESTMENTS

NOTE 4 EQUITY INVESTMENTS

Northern Border, Great Lakes and PNGTS are regulated by FERC and are operated by subsidiaries of TransCanada. The Partnership uses the equity method of accounting for its interests in its equity investees. The Partnership's equity investments are held through our ILPs that are considered to be variable interest entities (VIEs). Refer to Note 3, Accounting Pronouncements and Note 22, Variable Interest Entities.

		Equity Earnings from Unconsolidated Affiliates(b)			Investment in Unconsolidated Affiliates
		Year ended December 31			December 31
	Ownership Interest at December 31, 2016	Year ended December 31			December 31
(millions of dollars)	Ownership Interest at December 31, 2016	2016	2015	2014	2016	2015

Northern Border(a)	50.00%	69	66	69	444	480
Great Lakes	46.45%	28	31	19	474	485 (c)
PNGTS(d)	49.90%	19	–	–	126	–

		116	97	88	1,044	965


(a)	Equity earnings from Northern Border is net of the 12-year amortization of a $10 million transaction fee paid to the operator of Northern Border at the time of the Partnership's additional 20 percent acquisition in April 2006.
(b)	Equity Earnings represents our share in investee's earnings and does not include any impairment charge on the equity method investment recorded as a reduction of carrying value of these investments. Accordingly, no impairment charge was recorded by the Partnership on its equity investees for all the periods presented here except the impairment recognized in 2015 on our investment in Great Lakes as discussed below.
(c)	During the fourth quarter of 2015, we recognized an impairment charge on our investment in Great Lakes amounting to $199 million. See discussion below.
(d)	On January 1, 2016, the Partnership acquired a 49.9 percent interest in PNGTS (Refer to Note 6). For the year ended December 31, 2016, the Partnership recorded no undistributed earnings from PNGTS.

Northern Border

The Partnership, through its interest in TC PipeLines Intermediate Limited Partnership owns a 50 percent general partner interest in Northern Border. The other 50 percent partnership interest in Northern Border is held by ONEOK Partners, L.P., a publicly traded limited partnership. TC PipeLines Intermediate Limited Partnership, as one of the general partners, may be exposed to the commitments and contingencies of Northern Border. The Partnership holds a 98.9899 percent limited partnership interest in TC PipeLines Intermediate Limited Partnership.

Northern Border has a FERC-approved settlement agreement which established maximum long-term transportation rates and charges on the Northern Border system effective January 1, 2013. Northern Border is required to file for new rates no later than January 1, 2018.

The Partnership recorded no undistributed earnings from Northern Border for the years ended December 31, 2016, 2015 and 2014. At December 31, 2016 and 2015, the Partnership had a $116 million difference between the carrying value of Northern Border and the underlying equity in the net assets primarily resulting from the recognition and inclusion of goodwill in the Partnership's investment in Northern Border relating to the Partnership's April 2006 acquisition of an additional 20 percent general partnership interest in Northern Border. As of December 31, 2016, no impairment has been identified in our investment in Northern Border.

The summarized financial information for Northern Border is as follows:

December 31 (millions of dollars)		2016		2015

Assets
Cash and cash equivalents		14		27
Other current assets		36		33
Plant, property and equipment, net		1,089		1,124
Other assets(a)		14		16

		1,153		1,200

Liabilities and Partners' Equity
Current liabilities		38		39
Deferred credits and other		28		26
Long-term debt, net(a),(b)		430		409
Partners' equity
	Partners' capital	659		728
	Accumulated other comprehensive loss	(2	)	(2	)

		1,153		1,200


(a)	As a result of the application of ASU No. 2015-03 and similar to the presentation of debt discounts, debt issuance costs of $2 million at December 31, 2015 previously reported as other assets in the balance sheet were reclassified as an offset against their respective debt liabilities.
(b)	Includes current maturities of $100 million senior notes at December 31, 2015. During August 2016, the $100 million senior notes were refinanced with a draw on Northern Border's $200 million revolving credit agreement that expires in 2020.

Year ended December 31 (millions of dollars)	2016		2015		2014

Transmission revenues	292		286		293
Operating expenses	(72	)	(70	)	(72	)
Depreciation	(59	)	(60	)	(59	)
Financial charges and other	(21	)	(22	)	(22	)

Net income	140		134		140

Great Lakes

The Partnership, through its interest in TC GL Intermediate Limited Partnership owns a 46.45 percent general partner interest in Great Lakes. TransCanada owns the other 53.55 percent partnership interest. TC GL Intermediate Limited Partnership, as one of the general partners, may be exposed to the commitments and contingencies of Great Lakes. The Partnership holds a 98.9899 percent limited partnership interest in TC GL Intermediate Limited Partnership.

Great Lakes operates under rates established pursuant to a settlement approved by FERC in November 2013. Under the settlement, Great Lakes is required to file for new rates to be effective no later than January 1, 2018.

The Partnership recorded no undistributed earnings from Great Lakes for the years ended December 31, 2016, 2015, and 2014.

The Partnership made equity contributions to Great Lakes of $4 million and $5 million in the first and fourth quarter of 2016, respectively. These amounts represent the Partnership's 46.45 percent share of a $9 million and $10 million cash call from Great Lakes to make scheduled debt repayments.

During the fourth quarter of 2015, we have determined that our investment in Great Lakes' long-term value has been adversely impacted by the changing natural gas flows in its market region. Additionally, we have concluded that other strategic alternatives to increase its utilization or revenue were no longer feasible. As a result, we determined that the carrying value of our investment in Great Lakes was in excess of its fair value and the decline is not temporary. Accordingly, we concluded that the carrying value of our investment in Great Lakes was impaired.

Our analysis resulted in an impairment charge of $199 million reflected as Impairment of equity-method investment on our Statement of Income for the year ended December 31, 2015. The impairment charge reduced the difference between the carrying value of our investment in Great Lakes and the underlying equity in the net assets, to $260 million and the difference represents the equity method goodwill remaining in our investment in Great Lakes relating to the Partnership's February 2007 acquisition of a 46.45 percent general partner interest in Great Lakes.

The assumptions we used in 2015 related to the estimated fair value of our remaining equity investment in Great Lakes could be negatively impacted by near and long-term conditions including:


•	future regulatory rate action or settlement,
•	valuation of Great lakes in future transactions,
•	changes in customer demand at Great Lakes for pipeline capacity and services,
•	changes in North American natural gas production in the major producing basins,
•	changes in natural gas prices and natural gas storage market conditions, and
•	changes in other long-term strategic objectives.

Great Lakes' evolving market conditions and other factors relevant to Great Lakes' long term financial performance have remained relatively stable during the year. Accordingly, our estimation of the fair value of our investment in Great Lakes has not materially changed from 2015. There is a risk that reductions in future cash flow forecasts and other adverse changes in these key assumptions could result in additional future impairment of the carrying value of our investment in Great Lakes.

The summarized financial information for Great Lakes is as follows:

December 31 (millions of dollars)	2016	2015

Assets
Current assets	66	86
Plant, property and equipment, net	714	727

	780	813

Liabilities and Partners' Equity
Current liabilities	40	31
Long-term debt, net(a),(b)	278	297
Partners' equity	462	485

	780	813


(a)	The application of ASU No. 2015-03 did not have a material effect on Great Lakes' financial statements.
(b)	Includes current maturities of $19 million as of December 31, 2016 (December 31, 2015 – $19 million).

Year ended December 31 (millions of dollars)	2016		2015		2014

Transmission revenues	179		177		146
Operating expenses	(69	)	(59	)	(53)
Depreciation	(28	)	(28	)	(28)
Financial charges and other	(21	)	(23	)	(25)

Net income	61		67		40

PLANT, PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2016

PLANT, PROPERTY AND EQUIPMENT

NOTE 5 PLANT, PROPERTY AND EQUIPMENT

The following table includes plant, property and equipment of our consolidated entities:

	2016				2015
December 31 (millions of dollars)	Cost	Accumulated Depreciation		Net Book Value	Cost	Accumulated Depreciation		Net Book Value

Pipeline	2,091	(701	)	1,390	2,086	(638	)	1,448
Compression	519	(148	)	371	516	(134	)	382
Metering and other	159	(43	)	116	156	(39	)	117
Construction in progress	4	–		4	2	–		2

	2,773	(892	)	1,881	2,760	(811	)	1,949

ACQUISITIONS

12 Months Ended

Dec. 31, 2016

ACQUISITIONS

NOTE 6 ACQUISITIONS

PNGTS Acquisition

On January 1, 2016, the Partnership acquired a 49.9 percent interest in PNGTS from a subsidiary of TransCanada. The total purchase price of the PNGTS Acquisition was $228 million and consisted of $193 million in cash (including the final purchase price adjustment of $5 million) and the assumption of $35 million in proportional PNGTS debt.

The Partnership funded the cash portion of the transaction using proceeds received in 2015 from our ATM Program and additional borrowings under our Senior Credit Facility. The purchase agreement provides for additional payments to TransCanada ranging from $5 million up to a total of $50 million if pipeline capacity is expanded to various thresholds during the fifteen year period following the date of closing.

The acquisition was accounted for as a transaction between entities under common control, whereby the equity investment in PNGTS was recorded at TransCanada's carrying value and the total excess purchase price paid was recorded as a reduction in Partners' Equity.

The net purchase price was allocated as follows:

(millions of dollars)

Net Purchase Price(a)		193
Less: TransCanada's carrying value of PNGTS' net assets at January 1, 2016		120

Excess purchase price(b)		73


(a)	Total purchase price of $228 million less the assumption of $35 million of proportional PNGTS debt by the Partnership.
(b)	The excess purchase price of $73 million was recorded as a reduction in Partners' Equity.

2015 GTN Acquisition

On April 1, 2015, the Partnership acquired the remaining 30 percent interest in GTN from a subsidiary of TransCanada (2015 GTN Acquisition), which resulted in GTN being wholly-owned by the Partnership. The total purchase price of the 2015 GTN Acquisition was $446 million plus the final purchase price adjustment of $11 million, for a total of $457 million. The purchase price consisted of $264 million in cash (including the final purchase price adjustment of $11 million), the assumption of $98 million in proportional GTN debt and the issuance of 1,900,000 new Class B units to TransCanada valued at $50 each, representing a limited partner interest in the Partnership with a total value of $95 million.

The Partnership funded the cash portion of the transaction using a portion of the proceeds received on our March 13, 2015 debt offering (refer to Note 7). The Class B units entitle TransCanada to a distribution based on 30 percent of GTN's annual distributions as follows: (i) 100 percent of distributions above $20 million through March 31, 2020; and (ii) 25 percent of distributions above $20 million thereafter. Under the terms of the Third Amended and Restated Agreement of Limited Partnership of the Partnership (Partnership Agreement), the Class B distribution was initially calculated to equal 30 percent of GTN's distributable cash flow for the nine months ended December 31, 2015, less $15 million.

Prior to this transaction, the remaining 30 percent interest held by a subsidiary of TransCanada was reflected as a non-controlling interest in the Partnership's consolidated financial statements. The 2015 GTN Acquisition of this already-consolidated entity was accounted as a transaction between entities under common control, similar to a pooling of interests, whereby the acquired interest was recorded at TransCanada's carrying value and the total excess purchase price paid was recorded as a reduction in Partners' Equity.

The net purchase price was allocated as follows:

(millions of dollars)

Net Purchase Price(a)		359
Less: TransCanada's carrying value of non-controlling interest at April 1, 2015		232

Excess purchase price(b)		127


(a)	Total purchase price of $457 million less the assumption of $98 million of proportional GTN debt by the Partnership.
(b)	The excess purchase price of $127 million was recorded as a reduction in Partners' Equity.

Our General Partner also contributed approximately $2 million to maintain its effective two percent interest in the Partnership.

2014 Bison Acquisition

On October 1, 2014, the Partnership acquired the remaining 30 percent interest in Bison from a subsidiary of TransCanada. The total purchase price of the 2014 Bison Acquisition was $215 million plus purchase price adjustments of $2 million. The acquisition of Bison was financed through combinations of (i) net proceeds from the ATM Program (refer to Note 9), and (ii) short-term financing.

Prior to this transaction, the remaining 30 percent interest held by a subsidiary of TransCanada was reflected as non-controlling interest in the Partnership's consolidated financial statements. The 2014 Bison Acquisition of this already-consolidated entity was accounted as a transaction between entities under common control, similar to a pooling of interests, whereby the acquired interest was recorded at TransCanada's carrying value and the total excess purchase price paid was recorded as a reduction in Partners' Equity.

The purchase price was allocated as follows:

(millions of dollars)

Total cash consideration		217
TransCanada's carrying value of non-controlling interest at October 1, 2014		188

Excess purchase price		29

The excess purchase price of $29 million was recorded as a reduction in Partners' Equity.

DEBT AND CREDIT FACILITIES

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

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+ Details

DEBT AND CREDIT FACILITIES

12 Months Ended

Dec. 31, 2016

DEBT AND CREDIT FACILITIES

NOTE 7 DEBT AND CREDIT FACILITIES

(unaudited) (millions of dollars)		December 31, 2016	Weighted Average Interest Rate for the Year Ended December 31, 2016		December 31, 2015	Weighted Average Interest Rate for the Year Ended December 31, 2015

TC PipeLines, LP
	Senior Credit Facility due 2021	160	1.72%		200	1.44%
	2013 Term Loan Facility due 2018	500	1.73%		500	1.44%
	2015 Term Loan Facility due 2018	170	1.63%		170	1.47%
	4.65% Unsecured Senior Notes due 2021	350	4.65%	(b)	350	4.65%	(b)
	4.375% Unsecured Senior Notes due 2025	350	4.375%	(b)	350	4.375%	(b)
GTN
	5.29% Unsecured Senior Notes due 2020	100	5.29%	(b)	100	5.29%	(b)
	5.69% Unsecured Senior Notes due 2035	150	5.69%	(b)	150	5.69%	(b)
	Unsecured Term Loan Facility due 2019	65	1.43%		75	1.15%
Tuscarora
	Unsecured Term Loan due 2019	10	1.64%		–	–
	3.82% Series D Senior Notes due 2017	12	3.82%	(b)	16	3.82%	(b)

		1,867			1,911
Less: unamortized debt issuance costs and debt discount(a)		9			8
Less: current portion		23			14

		1,835			1,889


(a)	As a result of the application of ASU No. 2015-03 and similar to the presentation of debt discounts, debt issuance costs of $7 million at December 31, 2015 previously reported as other assets in the balance sheet were reclassified as an offset against debt. Refer to Note 3, Accounting Pronouncements.
(b)	Fixed interest rate.

On November 10, 2016, the Partnership's Senior Credit Facility was amended to extend the maturity period through November 10, 2021. The Facility consists of a $500 million senior revolving credit facility with a banking syndicate, under which $160 million was outstanding at December 31, 2016 (December 31, 2015 – $200 million), leaving $340 million available for future borrowing.

At the Partnership's option, the interest rate on the outstanding borrowings under the Senior Credit Facility may be lenders' base rate or the London Interbank Offered Rate (LIBOR) plus, in either case, an applicable margin that is based on the Partnership's long-term unsecured credit ratings. The Senior Credit Facility permits the Partnership to specify the portion of the borrowings to be covered by specific interest rate options and, for LIBOR-based borrowings, to specify the interest rate period. The Partnership is required to pay a commitment fee based on its credit rating and on the unused principal amount of the commitments under the Senior Credit Facility. The Senior Credit Facility has a feature whereby at any time, so long as no event of default has occurred and is continuing, the Partnership may request an increase in the Senior Credit Facility of up to $500 million, but no lender has an obligation to increase their respective share of the facility.

The LIBOR-based interest rate on the Senior Credit Facility was 1.92 percent at December 31, 2016 (December 31, 2015 – 1.50 percent).

On July 1, 2013, the Partnership entered into a term loan agreement with a syndicate of lenders for a $500 million term loan credit facility (2013 Term Loan Facility). On July 2, 2013, the Partnership borrowed $500 million under the 2013 Term Loan Facility, to pay a portion of the purchase price of the 2013 Acquisition, maturing on July 1, 2018. The 2013 Term Loan Facility bears interest based, at the Partnership's election, on the LIBOR or the base rate plus, in either case, an applicable margin. The base rate equals the highest of (i) SunTrust Bank's prime rate, (ii) 0.50 percent above the federal funds rate and (iii) 1.00 percent above one-month LIBOR. The applicable margin for the term loan is based on the Partnership's senior debt rating and ranges between 1.125 percent and 2.000 percent for LIBOR borrowings and 0.125 percent and 1.000 percent for base rate borrowings.

As of December 31, 2016, the variable interest rate exposure related to 2013 Term Loan Facility was hedged by fixed interest rate swap arrangements and our effective interest rate was 2.31 percent (2015-2.79 percent). Prior to hedging activities, the LIBOR-based interest rate was 1.87 percent at December 31, 2016 (December 31, 2015 – 1.50 percent).

On September 30, 2015, the Partnership entered into an agreement for a $170 million term loan credit facility (2015 Term Loan Facility). The Partnership borrowed $170 million under the 2015 Term Loan Facility to refinance its Short-Term Loan Facility which matured on September 30, 2015. The 2015 Term Loan Facility matures on October 1, 2018. The LIBOR-based interest rate on the 2015 Term Loan Facility was 1.77 percent at December 31, 2015 (December 31, 2015 – 1.39 percent).

The 2013 Term Loan Facility and the 2015 Term Loan Facility (Term Loan Facilities) and the Senior Credit Facility require the Partnership to maintain a certain leverage ratio (debt to adjusted cash flow [net income plus cash distributions received, extraordinary losses, interest expense, expense for taxes paid or accrued, and depreciation and amortization expense less equity earnings and extraordinary gains]) no greater than 5.00 to 1.00 for each fiscal quarter, except for the fiscal quarter and the two following fiscal quarters in which one or more acquisitions has been executed, in which case the leverage ratio is to be no greater than 5.50 to 1.00. The leverage ratio was 4.01 to 1.00 as of December 31, 2016.

The Senior Credit Facility and the Term Loan Facilities contain additional covenants that include restrictions on entering into mergers, consolidations and sales of assets, granting liens, material amendments to the Partnership Agreement, incurrence of additional debt by the Partnership's subsidiaries and distributions to unitholders. Upon any breach of these covenants, amounts outstanding under the Senior Credit Facility and the Term Loan Facilities may become immediately due and payable.

On March 13, 2015, the Partnership closed a $350 million public offering of senior unsecured notes bearing an interest rate of 4.375 percent maturing March 13, 2025. The net proceeds of $346 million were used to fund a portion of the 2015 GTN Acquisition (refer to Note 6) and to reduce the amount outstanding under our Senior Credit Facility. The indenture for the notes contains customary investment grade covenants.

On June 1, 2015, GTN's 5.09 percent unsecured Senior Notes matured. Also, on June 1, 2015, GTN entered into a $75 million unsecured variable rate term loan facility (Unsecured Term Loan Facility), which requires yearly principal payments until its maturity on June 1, 2019. The variable interest is based on LIBOR plus an applicable margin. The LIBOR-based interest rate on the Unsecured Term Loan Facility was 1.57 percent at December 31, 2016 (December 31, 2015 – 1.19 percent). GTN's Unsecured Senior Notes, along with this new Unsecured Term Loan Facility contain a covenant that limits total debt to no greater than 70 percent of GTN's total capitalization. GTN's total debt to total capitalization ratio at December 31, 2016 is 44.5 percent.

Tuscarora's Series D Senior Notes, which require yearly principal payments until maturity, are secured by Tuscarora's transportation contracts, supporting agreements and substantially all of Tuscarora's property. The note purchase agreements contain certain provisions that include, among other items, limitations on additional indebtedness and distributions to partners. The Series D Senior Notes contain a covenant that limits total debt to no greater than 45 percent of Tuscarora's total capitalization. Tuscarora's total debt to total capitalization ratio at December 31, 2016 was 21.22 percent. Additionally, the Series D Senior Notes require Tuscarora to maintain a Debt Service Coverage Ratio (cash available from operations divided by a sum of interest expense and principal payments) of greater than 3.00 to 1.00. The ratio was 4.15 to 1.00 as of December 31, 2016.

On April 29, 2016, Tuscarora entered into a $9.5 million unsecured variable rate term loan facility which requires yearly principal payments until its maturity on April 29, 2019. The variable interest is based on LIBOR plus an applicable margin and was 1.90 percent at December 31, 2016.

At December 31, 2016, the Partnership was in compliance with its financial covenants, in addition to the other covenants which include restrictions on entering into mergers, consolidations and sales of assets, granting liens, material amendments to the Partnership Agreement, incurring additional debt and distributions to unitholders.

The principal repayments required by the Partnership on its debt are as follows:

(millions of dollars)

2017		23
2018		691
2019		43
2020		100
2021		510
Thereafter		500

		1,867

OTHER LIABILITIES

12 Months Ended

Dec. 31, 2016

OTHER LIABILITIES

OTHER LIABILITIES

NOTE 8 OTHER LIABILITIES

December 31 (millions of dollars)	2016	2015

Regulatory liabilities	25	24
Other liabilities	3	3

	28	27

The Partnership collects estimated future removal costs related to its transmission and gathering facilities in its current rates and recognizes regulatory liabilities in this respect in the balance sheet. Estimated costs associated with the future removal of transmission and gathering facilities are collected through depreciation as allowed by FERC. These amounts do not represent asset retirement obligations as defined by FASB ASC 410, Accounting for Asset Retirement Obligations.

PARTNERS' EQUITY	12 Months Ended
PARTNERS' EQUITY	Dec. 31, 2016
PARTNERS' EQUITY
PARTNERS' EQUITY	NOTE 9 PARTNERS' EQUITY At December 31, 2016, the Partnership had 67,454,831common units outstanding, of which 50,370,000 were held by non-affiliates and 17,084,831 common units were held by subsidiaries of TransCanada, including 5,797,106 common units held by our General Partner. Additionally, TransCanada, through our General Partner, owns 100 percent of our IDRs and an effective two percent general partner interest in the Partnership. TransCanada also holds 100 percent of our 1,900,000 outstanding Class B units. ATM Equity Issuance Program (ATM Program) In August 2014, the Partnership launched its $200 million ATM program pursuant to which, the Partnership may from time to time, offer and sell, through sales agents, common units, representing limited partner interests. On August 5, 2016, the Partnership entered into a new $400 million Equity Distribution Agreement (EDA) with five financial institutions (the Managers). Sales of the common units will be issued pursuant to the Partnership's shelf registration statement on Form S-3 (Registration No. 333-211907), which was declared effective by the SEC on August 4, 2016. In 2016, the Partnership issued 3.1 million common units under the ATM Program generating net proceeds of approximately $164 million, plus an additional $3 million from the General Partner's to maintain its effective two percent interest. The commissions to our sales agents were approximately $2 million. The net proceeds were used to repay a portion of the borrowings under the Senior Credit Facility for the PNGTS Acquisition and for general partnership purposes. The 3.1 million common units issued include the 1.6 million common units subject to rescission as discussed below. In 2015, the Partnership issued 0.7 million common units under the ATM Program generating net proceeds of approximately $43 million, plus an additional $1 million from the General Partner's to maintain its effective two percent interest. The commissions to our sales agents were approximately $0.4 million. The net proceeds were used for general partnership purposes. In 2014, the Partnership issued 1.3 million common units under the ATM Program generating net proceeds of approximately $71 million, plus an additional $2 million from the General Partner's to maintain its effective two percent interest. The commissions to our sales agents were approximately $1 million. The net proceeds were used to finance the 2014 Bison Acquisition (refer to Note 6). Common unit issuance subject to rescission On July 17, 2014, the SEC declared effective a registration statement (the Registration Statement) that we had filed to cover sales of Common Units under our ATM program. On February 26, 2016, at the time of the filing of the 2015 Form 10-K, we believed that the Partnership continued to be eligible to use the effective Registration Statement to sell Common Units under our ATM program. However, we were advised by the SEC on June 23, 2016 that as a result of the untimely filing of an employee-related Form 8-K on October 28, 2015, which was not filed via EDGAR until 6:02 p.m. Eastern Time (32 minutes after the 5:30 p.m. Eastern Time cutoff), the Partnership was ineligible to use the Registration Statement after the filing of the 2015 Form 10-K. Because the Partnership was ineligible to continue using the Registration Statement following the filing of the 2015 Form 10-K, it is possible that the sales of an aggregate 1,619,631 Common Units under the Registration Statement (the ATM Common Units), which were sold between March 8, 2016 and May 19, 2016 at per Common Unit prices ranging from $47.00 to $54.95, may be deemed to have been unregistered sales of securities. If it is determined that persons who purchased the ATM Common Units from the Partnership after February 26, 2016, purchased such Common Units in an offering deemed to be unregistered, then to the extent there may have been a violation of federal securities laws such persons may be entitled to rescission rights, pursuant to which they could be entitled to recover the amount paid for such ATM Common Units, plus interest (based on the statutory rate under applicable state law), less the amount of any distributions. If such investor has sold any of the ATM Common Units purchased by the investor, then the investor would be entitled to recover the difference between the amount paid for such ATM Common Units and the amount at which such ATM Common Units were sold, assuming the investor's ATM Common Units were sold at a loss, plus interest and less the amount of any distributions. If all of the investors who purchased the ATM Common Units from the Partnership after February 26, 2016 continue to own all of the ATM Common Units and were to demand rescission of their purchases, and such investors were in fact found to be entitled to such rescission, then we would be obligated to repay approximately $82,334,015, plus interest, less the amount of any distributions. The Securities Act generally requires that any claim brought for a violation of Section 5 of the Securities Act be brought within one year of the violation. No unitholder has claimed or attempted to exercise any rescission rights to date. At December 31, 2016, the Partnership classified all the 1.6 million common units issued under its ATM program after February 26, 2016 up to and including May 19, 2016, which may be subject to rescission rights, outside of equity given the potential redemption feature which is not within the control of the Partnership. These units are treated as outstanding for financial reporting purposes. The total amount transferred outside of equity was approximately $83 million which includes interest, less distributions paid, and includes our General Partner's share to maintain its effective two percent interest. Issuance of Class B units On April 1, 2015, we issued Class B units to TransCanada to finance a portion of the 2015 GTN Acquisition. The Class B units entitle TransCanada to an annual distribution which is an amount based on 30 percent of cash distributions from GTN exceeding certain annual thresholds (refer to Note 6). The Class B units contain no mandatory or optional redemption features and are also non-convertible, non-exchangeable, non-voting and rank equally with common units upon liquidation. The Class B units' equity account is increased by the excess of 30 percent of GTN's distributions over the annual threshold until such amount is declared for distribution and paid every first quarter of the subsequent year. For the year ended December 31, 2016 and 2015, the Class B units' equity account was increased by $22 million and $12 million, respectively. These amounts equal 30 percent of GTN's total distributable cash flow above the $20 million threshold in 2016 and $15 million in 2015 (refer to Notes 12 and 13).

ACCUMULATED OTHER COMPREHENSIVE LOSS

12 Months Ended

Dec. 31, 2016

ACCUMULATED OTHER COMPREHENSIVE LOSS

ACCUMULATED OTHER COMPREHENSIVE LOSS

NOTE 10 ACCUMULATED OTHER COMPREHENSIVE LOSS

The changes in accumulated other comprehensive loss (AOCL) by components are as follows:

(millions of dollars)		Cash flow hedges

Balance at December 31, 2013		(1)
Other comprehensive loss before reclassifications		(1)
Amounts reclassified from AOCL		–

Net other comprehensive loss		(1)

Balance at December 31, 2014		(2)
Other comprehensive loss before reclassifications		–
Amounts reclassified from AOCL		–

Net other comprehensive loss		–

Balance at December 31, 2015		(2)
Other comprehensive income before reclassifications		3
Amounts reclassified from AOCL		(1)

Net other comprehensive loss		2

Balance as of December 31, 2016		–

FINANCIAL CHARGES AND OTHER

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e716-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e709-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e637-108580

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e681-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details

FINANCIAL CHARGES AND OTHER

12 Months Ended

Dec. 31, 2016

FINANCIAL CHARGES AND OTHER

NOTE 11 FINANCIAL CHARGES AND OTHER

Year ended December 31 (millions of dollars)	2016		2015		2014

Interest expense(a)	65		59		49
Net realized loss related to the interest rate swaps	3		2		2
Other	(1	)	(5	)	(1	)

	67		56		50


(a)	Effective January 1, 2016, interest expense includes amortization of debt issuance costs and discount costs. Refer to Note 3.

NET INCOME (LOSS) PER COMMON UNIT

12 Months Ended

Dec. 31, 2016

NET INCOME (LOSS) PER COMMON UNIT

NET INCOME (LOSS) PER COMMON UNIT

NOTE 12 NET INCOME (LOSS) PER COMMON UNIT

Net income (loss) per common unit is computed by dividing net income attributable to controlling interests, after deduction of amounts attributable to the General Partner and Class B units, by the weighted average number of common units outstanding.

The amounts allocable to the General Partner equals an amount based upon the General Partner's effective two percent general partner interest, plus an amount equal to incentive distributions. Incentive distributions are paid to the General Partner if quarterly cash distributions on the common units exceed levels specified in the Partnership Agreement (refer to Note 13).

The amount allocable to the Class B units in 2016 equals an amount based upon 30 percent of GTN's distributable cash flow during the year ended December 31, 2016 less $20 million (2015 – $15 million).

Net income (loss) per common unit was determined as follows:

(millions of dollars, except per common unit amounts)	2016		2015		2014

Net income attributable to controlling interests	244		13		172
Net income attributable to General Partner	(4	)	–		(3	)
Incentive distributions attributable to the General Partner(a)	(7	)	(3	)	(1	)
Net income attributable to the Class B units(b)	(22	)	(12	)	–

Net income (loss) attributable to common units	211		(2	)	168

Weighted average common units outstanding (millions) – basic and diluted	65.7	(c)	63.9		62.7
Net income (loss) per common unit – basic and diluted	$ 3.21		$ (0.03	)	$ 2.67


(a)	Under the terms of the Partnership Agreement, for any quarterly period, the participation of the incentive distribution rights (IDRs) is limited to the available cash distributions declared. Accordingly, incentive distributions allocated to the General Partner are based on the Partnership's available cash during the current reporting period, but declared and paid in the subsequent reporting period.
(b)	As discussed in Note 9, the Class B units entitle TransCanada to a distribution which is an amount based on 30 percent of GTN's distributions after exceeding certain annual thresholds. The distribution will be payable in the first quarter with respect to the prior year's distributions. Consistent with the application of Accounting Standards Codification (ASC) Topic 260 – "Earnings per share", the Partnership allocated a portion of net income attributable to controlling interests to the Class B units in an amount equal to 30 percent of GTN's total distributable cash flows during the year ended December 31, 2016 less the threshold level of $20 million (2015 – less $15 million). During the year ended December 31, 2016, 30 percent of GTN's total distributable cash flow was $42 million. As a result of exceeding the threshold level of $20 million, $22 million of net income attributable to controlling interests was allocated to the Class B units at December 31, 2016 (2015 – $12 million). Refer to Note 9.
(c)	Includes the common units subject to rescission. These units are treated as outstanding for financial reporting purposes. Refer to Note 9.

CASH DISTRIBUTIONS

12 Months Ended

Dec. 31, 2016

CASH DISTRIBUTIONS

CASH DISTRIBUTIONS

NOTE 13 CASH DISTRIBUTIONS

The Partnership makes cash distributions to its partners with respect to each calendar quarter within 45 days after the end of each quarter. Distributions are based on Available Cash, as defined in the Partnership Agreement, which includes all cash and cash equivalents of the Partnership and working capital borrowings less reserves established by the General Partner.

Pursuant to the Partnership Agreement, the General Partner receives two percent of all cash distributions in regard to its general partner interest and is also entitled to incentive distributions as described below. The unitholders receive the remaining portion of the cash distribution.

The following table illustrates the percentage allocations of available cash from operating surplus between the common unitholders and our General Partner based on the specified target distribution levels. The percentage interests set forth below for our General Partner include its two percent general partner interest and IDRs, and assume our General Partner has contributed any additional capital necessary to maintain its two percent general partner interest. The distribution to the General Partner illustrated below, other than in its capacity as a holder of 5,797,106 common units that are in excess of its effective two percent general partner interest, represents the IDRs.

		Marginal Percentage Interest in Distribution
	Total Quarterly Distribution Per Unit Target Amount	Common Unitholders	General Partner

Minimum Quarterly Distribution	$0.45	98%	2%
First Target Distribution	above $0.45 up to $0.81	98%	2%
Second Target Distribution	above $0.81 up to $0.88	85%	15%
Thereafter	above $0.88	75%	25%

The following table provides information about our distributions (in millions, except per unit distributions amounts).

					Limited Partners			General Partner
Declaration Date		Payment Date		Per Unit Distribution	Common Units	Class B Units(c)		2%	IDRs(a)	Total Cash Distribution

1/16/2014		2/14/2014		$ 0.81	$ 50	$ –		$ 1	$–	$ 51
4/25/2014		5/15/2014		$ 0.81	$ 51	$ –		$ 1	$–	$ 52
7/23/2014		8/14/2014		$ 0.84	$ 53	$ –		$ 1	$–	$ 54
10/23/2014		11/14/2014		$ 0.84	$ 53	$ –		$ 1	$ 1	$ 55
1/22/2015		2/13/2015		$ 0.84	$ 54	$ –		$ 1	$–	$ 55
4/23/2015		5/15/2015		$ 0.84	$ 54	$ –		$ 1	$–	$ 55
7/23/2015		8/14/2015		$ 0.89	$ 56	$ –		$ 2	$ 1	$ 59
10/22/2015		11/13/2015		$ 0.89	$ 57	$ –		$ 1	$ 1	$ 59
1/21/2016		2/12/2016		$ 0.89	$ 57	$ 12	(d)	$ 1	$ 1	$ 71
4/21/2016		5/13/2016		$ 0.89	$ 58	$ –		$ 1	$ 1	$ 60
7/21/2016		8/12/2016		$ 0.94	$ 62	$ –		$ 1	$ 2	$ 65
10/20/2016		11/14/2016		$ 0.94	$ 63	$ –		$ 1	$ 2	$ 66
1/23/2017	(b)	2/14/2017	(b)	$ 0.94	$ 64	$ 22	(e)	$ 2	$ 2	$ 90


(a)	The distributions paid for the year ended December 31, 2016 included incentive distributions to the General Partner of $6 million (2015 – $2 million, 2014 – $1 million).
(b)	On February 14, 2017, we paid a cash distribution of $0.94 per unit on our outstanding common units to unitholders of record at the close of business on February 2, 2017 (refer to Note 23).
(c)	The Class B units issued by us on April 1, 2015 represent limited partner interests in us and entitle TransCanada to an annual distribution which is an amount based on 30 percent of GTN's annual distributions after exceeding certain annual thresholds (refer to Note 6 and 9).
(d)	On February 12, 2016, we paid TransCanada $12 million representing 30 percent of GTN's total distributable cash flows for the nine months ended December 31, 2015 less $15 million.
(e)	On February 14, 2017, we paid TransCanada $22 million representing 30 percent of GTN's total distributable cash flows for the year ended December 31, 2016 less $20 million (refer to Note 9 and 23).

CHANGE IN OPERATING WORKING CAPITAL

12 Months Ended

Dec. 31, 2016

CHANGE IN OPERATING WORKING CAPITAL

CHANGE IN OPERATING WORKING CAPITAL

NOTE 14 CHANGE IN OPERATING WORKING CAPITAL

Year Ended December 31 (millions of dollars)	2016		2015		2014

Change in accounts receivable and other	(3	)	(1	)	1
Change in other current assets	(3	)	1		1
Change in accounts payable and accrued liabilities(a)	5		(3	)	4
Change in accounts payable to affiliates	2		(10)	(b)	11
Change in accrued interest	1		4		–

Change in operating working capital	2		(9	)	17


(a)	The accrual of $10 million for the construction of GTN's Carty Lateral in December 31, 2015 was paid during the first quarter 2016. Accordingly, the payment was reported as capital expenditures in our cash flow statement during 2016.
(b)	Excludes certain non-cash items primarily related to accruals of $10 million for construction of GTN's Carty Lateral and $2 million of costs related to acquisition of 49.9 percent interest in PNGTS (Refer to Note 6).

TRANSACTIONS WITH MAJOR CUSTOMERS

12 Months Ended

Dec. 31, 2016

TRANSACTIONS WITH MAJOR CUSTOMERS

TRANSACTIONS WITH MAJOR CUSTOMERS

NOTE 15 TRANSACTIONS WITH MAJOR CUSTOMERS

The following table shows revenues from the Partnership's major customers comprising more than 10 percent of the Partnership's total revenues for the years ended December 31, 2016, 2015 and 2014:

Year Ended December 31 (millions of dollars)	2016	2015	2014

Anadarko Energy Services Company (Anadarko)	48	48	48
Pacific Gas and Electric Company (Pacific Gas)	36	42	45

At December 31, 2016, Anadarko owed the Partnership approximately $4 million, which is greater than 10 percent of our Trade accounts receivable. At December 31, 2015, Anadarko and Pacific Gas each owed the Partnership approximately $4 million and $3 million, respectively, which is greater than 10 percent of our Trade accounts receivable.

RELATED PARTY TRANSACTIONS

12 Months Ended

Dec. 31, 2016

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS

NOTE 16 RELATED PARTY TRANSACTIONS

The Partnership does not have any employees. The management and operating functions are provided by the General Partner. The General Partner does not receive a management fee in connection with its management of the Partnership. The Partnership reimburses the General Partner for all costs of services provided, including the costs of employee, officer and director compensation and benefits, and all other expenses necessary or appropriate to the conduct of the business of, and allocable to, the Partnership. Such costs include (i) overhead costs (such as office space and equipment) and (ii) out-of-pocket expenses related to the provision of such services. The Partnership Agreement provides that the General Partner will determine the costs that are allocable to the Partnership in any reasonable manner determined by the General Partner in its sole discretion. Total costs charged to the Partnership by the General Partner were $3 million for each of the years ended December 31, 2016, 2015 and 2014.

As operator, TransCanada's subsidiaries provide capital and operating services to GTN, Northern Border, PNGTS, Bison, Great Lakes, North Baja and Tuscarora (together, "our pipeline systems"). TransCanada's subsidiaries incur costs on behalf of our pipeline systems, including, but not limited to, employee salary and benefit costs, and property and liability insurance costs.

Capital and operating costs charged to our pipeline systems for the years ended December 31, 2016, 2015 and 2014 by TransCanada's subsidiaries and amounts payable to TransCanada's subsidiaries at December 31, 2016 and 2015 are summarized in the following tables:

Year ended December 31 (millions of dollars)		2016	2015	2014

Capital and operating costs charged by TransCanada's subsidiaries to:
	Great Lakes(a)	30	30	30
	Northern Border(a)	32	36	35
	PNGTS(a)(b)	8	–	–
	GTN(a)(c)	27	30	30
	Bison(a)(d)	2	4	6
	North Baja	4	5	5
	Tuscarora	5	4	4
Impact on the Partnership's net income attributable to controlling interests:
	Great Lakes	13	13	13
	Northern Border	12	14	16
	PNGTS(b)	4	–	–
	GTN(c)	24	25	19
	Bison(d)	3	4	4
	North Baja	4	5	4
	Tuscarora	4	4	4

December 31 (millions of dollars)		2016	2015

Amount payable to TransCanada's subsidiaries for costs charged in the year by:
	Great Lakes(a)	4	3
	Northern Border(a)	4	5
	PNGTS(a)	1	–
	GTN	3	3
	Bison	1	–
	North Baja	1	–
	Tuscarora	1	1


(a)	Represents 100 percent of the costs.
(b)	In 2016, the Partnership acquired a 49.9 percent interest in PNGTS (Refer to Note 6).
(c)	In 2015, the Partnership acquired the remaining 30 percent interest in GTN (Refer to Note 6).
(d)	In 2014, the Partnership acquired the remaining 30 percent interest in Bison (Refer to Note 6).

Great Lakes earns significant transportation revenues from TransCanada and its affiliates, some of which are provided at discounted rates and some at maximum recourse rates. For the year ended December 31, 2016, Great Lakes earned 68 percent of its transportation revenues from TransCanada and its affiliates (2015 – 71 percent; 2014 – 49 percent). Additionally, Great Lakes earned approximately one percent of its total revenues as affiliated rental revenue in 2016 (2015 – 1 percent and 2014 – 1 percent).

At December 31, 2016, $19 million was included in Great Lakes' receivables in regards to the transportation contracts with TransCanada and its affiliates (December 31, 2015 – $17 million).

Great Lakes operates under a FERC approved 2013 rate settlement that includes a revenue sharing mechanism that requires Great Lakes to share with its shippers certain percentages of any qualifying revenues earned above a certain ROEs. A refund of $2.5 million was paid to shippers in 2016 relating to the year ended December 31, 2015, of which approximately 85 percent was made to affiliates of Great Lakes. For the year ended December 31, 2016, Great Lakes has recorded an estimated revenue sharing provision amounting to $7.2 million and Great Lakes expects that a significant percentage of the refund will be to its affiliates as well.

Great Lakes has a cash management agreement with TransCanada whereby Great Lakes' funds are pooled with other TransCanada affiliates. The agreement also gives Great Lakes the ability to obtain short-term borrowings to provide liquidity for Great Lakes' operating needs. At December 31, 2016 and 2015, Great Lakes has an outstanding receivable from this arrangement amounting to $27 million and $51 million, respectively.

Effective November 1, 2014, Great Lakes executed contracts with an affiliate, ANR Pipeline Company (ANR), to provide firm service in Michigan and Wisconsin. These contracts were at the maximum FERC authorized rate and were intended to replace historical contracts. On December 3, 2014, FERC accepted and suspended Great Lakes' tariff records to become effective May 3, 2015, subject to refund. On February 2, 2015, FERC issued an Order granting a rehearing and clarification request submitted by Great Lakes, which allowed additional time for FERC to consider Great Lakes' request. Following extensive discussions with numerous shippers and other stakeholders, on April 20, 2015, ANR filed a settlement with FERC that included an agreement by ANR to pay Great Lakes the difference between the historical and maximum rates (ANR Settlement). Great Lakes provided service to ANR under multiple service agreements and rates through May 3, 2015 when Great Lakes' tariff records became effective and subject to refund. Great Lakes deferred an approximate $9 million of revenue related to services performed in 2014 and approximately $14 million of additional revenue related to services performed through May 3, 2015 under such agreements. On October 15, 2015, FERC accepted and approved the ANR Settlement. As a result, Great Lakes recognized the deferred transportation revenue of approximately $23 million in the fourth quarter of 2015.

QUARTERLY FINANCIAL DATA (unaudited)

12 Months Ended

Dec. 31, 2016

QUARTERLY FINANCIAL DATA (unaudited)

QUARTERLY FINANCIAL DATA (unaudited)

NOTE 17 QUARTERLY FINANCIAL DATA (unaudited)

The following sets forth selected unaudited financial data for the four quarters in 2016 and 2015:

Quarter ended (millions of dollars except per common unit amounts)	Mar 31	Jun 30	Sept 30	Dec 31

2016
Transmission revenues	86	89	91	91
Equity earnings(a)(c)	42	22	24	28
Net income	73	54	58	60
Net income attributable to controlling interests	73	54	58	60
Net income per common unit	$ 1.10	$ 0.76	$ 0.65	$ 0.70
Cash distribution paid	71	60	65	66

2015
Transmission revenues	87	85	83	89
Equity earnings(a)	31	15	17	34
Impairment of equity-method investment(b)	–	–	–	(199	)
Net income (loss)	64	44	49	(137	)
Net income (loss) attributable to controlling interests	57	44	49	(137	)
Net income (loss) per common unit	$ 0.88	$ 0.66	$ 0.70	$ (2.24	)
Cash distribution paid	55	55	59	59


(a)	Equity Earnings represents our share in investee's earnings and does not include any impairment charge on equity method goodwill included as part of the carrying value of our equity investments.
(b)	During the three months ended December 31, 2015, we recognized an impairment charge on our investment in Great Lakes amounting to $199 million. During the year ended December 31, 2015, no impairment has been identified on our investment in Northern Border (Refer to Note 4).
(c)	During the year ended December 31, 2016, no impairment has been identified related to our equity investments in Northern Border, Great Lakes or PNGTS.

FAIR VALUE MEASUREMENTS

12 Months Ended

Dec. 31, 2016

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS

NOTE 18 FAIR VALUE MEASUREMENTS

(a) Fair Value Hierarchy

Under ASC 820, Fair Value Measurements and Disclosures, fair value measurements are characterized in one of three levels based upon the input used to arrive at the measurement. The three levels of the fair value hierarchy are as follows:


•	Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access at the measurement date.
•	Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.
•	Level 3 inputs are unobservable inputs for the asset or liability.

When appropriate, valuations are adjusted for various factors including credit considerations. Such adjustments are generally based on available market evidence. In the absence of such evidence, management's best estimate is used.

(b) Fair Value of Financial Instruments

The carrying value of cash and cash equivalents, accounts receivable and other, accounts payable and accrued liabilities, accounts payable to affiliates, accrued interest and short-term debt approximate their fair values because of the short maturity or duration of these instruments, or because the instruments bear a variable rate of interest or a rate that approximates current rates. The fair value of the Partnership's long-term debt is estimated by discounting the future cash flows of each instrument at estimated current borrowing rates. The fair value of interest rate derivatives is calculated using the income approach which uses period-end market rates and applies a discounted cash flow valuation model.

The Partnership has classified the fair value of natural gas imbalances as a Level 2 of the fair value hierarchy for fair value disclosure purposes, as the valuation approach includes quoted prices in the market index and observable volumes for the imbalance.

Long-term debt is recorded at amortized cost and classified in Level 2 of the fair value hierarchy for fair value disclosure purposes. Interest rate derivative assets and liabilities are classified in Level 2 for all periods presented where the fair value is determined by using valuation techniques that refer to observable market data or estimated market prices. The estimated fair value of the Partnership's debt as at December 31, 2016 and December 31, 2015 was $1,908 million and $1,873 million, respectively.

The ATM common units which may be subject to rescission rights, as discussed more fully in Note 9, were measured using the original issuance price, plus statutory interest and less any distributions paid. This fair value measurement is classified as Level 2.

Market risk is the risk that changes in market interest rates may result in fluctuations in the fair values or cash flows of financial instruments. The Partnership's floating rate debt is subject to LIBOR benchmark interest rate risk. The Partnership uses interest rate derivatives to manage its exposure to interest rate risk. We regularly assess the impact of interest rate fluctuations on future cash flows and evaluate hedging opportunities to mitigate our interest rate risk.

The interest rate swaps are structured such that the cash flows of the derivative instruments match those of the variable rate of interest on the 2013 Term Loan Facility. The Partnership hedged interest payments on the variable-rate 2013 Term Loan Facility with interest rate swaps maturing July 1, 2018, at a weighted average fixed interest rate of 2.31 percent. At December 31, 2016, the fair value of the interest rate swaps accounted for as cash flow hedges was an asset of $1 million and a liability of $1 million (on a gross basis) and an asset of nil million (on a net basis). At December 31, 2015, the fair value of the interest rate swaps accounted for as cash flow hedges was a liability of $1 million both on a gross and net basis. The Partnership did not record any amounts in net income related to ineffectiveness for interest rate hedges for the years ended December 31, 2016, 2015 and 2014. The net change in fair value of interest rate derivative instruments recognized in other comprehensive income was a gain of $2 million for the year ended December 31, 2016 (2015 – nil million, 2014 – loss of $1 million). In 2016, the net realized loss related to the interest rate swaps was $3 million, and was included in financial charges and other (2015 – $2 million, 2014 – $2 million). Refer to Note 11 – Financial Charges and Other.

The Partnership has no master netting agreements, however, contracts contain provisions with rights of offset. The Partnership has elected to present the fair value of derivative instruments with the right to offset on a gross basis in the balance sheet. Had the Partnership elected to present these instruments on a net basis, there would be net asset of nil million as of December 31, 2016 and there would be no effect on the consolidated balance sheet as of December 31, 2015.

Our maximum counterparty credit exposure with respect to financial instruments at the balance sheet date consists primarily of the carrying amount, which approximates fair value, of non-derivative financial assets, such as cash and cash equivalents and receivables, as well as the fair value of derivative financial assets. We review our accounts receivable regularly and record allowances for doubtful accounts using the specific identification method. At December 31, 2016, we had not incurred any significant credit losses and had no significant amounts past due or impaired. At December 31, 2016, we had a credit risk concentration on one of our customers and the amount owed is greater than 10 percent of our trade accounts receivable (refer to Note 15).

The estimated fair value measurements on Tuscarora (refer to Note 20) and our equity investment in Great Lakes (refer to Note 4) are both classified as Level 3. In the determination of the fair value, we used internal forecasts on expected future cash flows and applied appropriate discount rates. The determination of expected future cash flows involved significant assumptions and estimates as discussed more fully on Notes 4 and 20.

ACCOUNTS RECEIVABLE AND OTHER

12 Months Ended

Dec. 31, 2016

ACCOUNTS RECEIVABLE AND OTHER

ACCOUNTS RECEIVABLE AND OTHER

NOTE 19 ACCOUNTS RECEIVABLE AND OTHER

December 31 (millions of dollars)	2016	2015

Trade accounts receivable, net of allowance of nil	34	32
Imbalance receivable from affiliates	2	1
Other	1	–

	37	33

GOODWILL AND REGULATORY	12 Months Ended
GOODWILL AND REGULATORY	Dec. 31, 2016
GOODWILL AND REGULATORY
GOODWILL AND REGULATORY	NOTE 20 GOODWILL AND REGULATORY Tuscarora – On January 21, 2016, FERC issued an Order initiating an investigation pursuant to Section 5 of the Natural Gas Act of 1938 (NGA) to determine whether Tuscarora's existing rates for jurisdictional services are just and reasonable. On July 22, 2016, Tuscarora filed a petition with FERC requesting approval of the Stipulation and Agreement of Settlement (Tuscarora Settlement) Tuscarora made with its customers. On September 22, 2016, FERC approved the Tuscarora Settlement that resolved the Section 5 rate review initiated by FERC in January 2016. Under the terms of the Tuscarora Settlement, Tuscarora's system-wide unit rate initially decreased by 17 percent, effective August 1, 2016. Unless superseded by a subsequent rate case or settlement, this rate will remain in effect until July 31, 2019, after which time the unit rate will decrease an additional seven percent from August 1, 2019 through July 31, 2022. The settlement does not contain a rate moratorium and requires Tuscarora to file to establish new rates no later than August 1, 2022. The reduction in Tuscarora's future cash flows as a result of the Tuscarora Settlement constituted a triggering event in the second quarter of 2016 that led us to evaluate, for possible impairment, the $82 million of goodwill related to our acquisition of Tuscarora. Our second quarter analysis, which was also reviewed for any material updates as part of our annual impairment test on goodwill, resulted in the estimated fair value of Tuscarora exceeding its carrying value but the excess was less than 10 percent. The fair value was measured using a discounted cash flow analysis and included revenues expected from Tuscarora's current and expected future contracting level. There is a risk that reductions in future cash flow forecasts as a result of Tuscarora not being able to maintain its current contracting level and/or not being able to realize other opportunities on the system, together with adverse changes in other key assumptions such as expected outcome of future rate proceedings, projected operating costs and estimated rate of return on invested capital, could result in a future impairment of the goodwill balance relating to Tuscarora. North Baja – On January 6, 2017, North Baja notified FERC that current market conditions do not support the replacement of the compression that was temporarily abandoned in 2013 and requested authorization to permanently abandon two compressor units and a nominal volume of unsubscribed firm capacity. The requested abandonments will not have any impact on existing firm transportation service. GTN – GTN operates under rates established pursuant to a settlement approved by FERC in June 2015. Beginning in January 2016, GTN's rates decreased by 10 percent and will continue in effect through December 31, 2019. Unless superseded by a subsequent rate case or settlement, GTN's rates will decrease an additional eight percent for the period January 1, 2020 through December 31, 2021 when GTN will be required to establish new rates.

CONTINGENCIES	12 Months Ended
CONTINGENCIES	Dec. 31, 2016
CONTINGENCIES
CONTINGENCIES	NOTE 21 CONTINGENCIES The Partnership and its pipeline systems are subject to various legal proceedings in the ordinary course of business. Our accounting for contingencies covers a variety of business activities, including contingencies for legal and environmental liabilities. The Partnership accrues for these contingencies when the assessments indicate that it is probable that a liability has been incurred or an asset will not be recovered and an amount can be reasonably estimated in accordance with ASC 450 – Contingencies. We base these estimates on currently available facts and the estimates of the ultimate outcome or resolution. Actual results may differ from estimates resulting in an impact, positive or negative, on earnings and cash flow. Contingencies that might result in a gain are not accrued in our consolidated financial statements. Below are the material legal proceedings that might have a significant impact on the Partnership: Great Lakes v. Essar Steel Minnesota LLC, et al. – On October 29, 2009, Great Lakes filed suit in the U.S. District Court, District of Minnesota, against Essar Minnesota LLC (Essar Minnesota) and certain Foreign Essar Affiliates (collectively, Essar) for breach of its monthly payment obligation under its transportation services agreement with Great Lakes. Great Lakes sought to recover approximately $33 million for past and future payments due under the agreement. On September 16, 2015, following a jury trial, the federal district court judge entered a judgment in the amount of $32.9 million in favor of Great Lakes. On September 20, 2015, Essar appealed the decision to the United States Court of Appeals for the Eighth Circuit (Eighth Circuit) based on an allegation of improper jurisdiction and a number of other rulings by the federal district judge. Essar was required to post a performance bond for the full value of the judgment pending appeal. In July 2016, Essar Minnesota filed for Bankruptcy. The Foreign Essar Affiliates have not filed for bankruptcy. The Eighth Circuit heard the appeal on October 20, 2016. A decision on the appeal was received in December 2016 and the Eighth Circuit vacated Great Lakes' judgment against Essar finding that there was no federal jurisdiction. Great Lakes filed a Request for Rehearing with the Eighth Circuit and it was denied in January 2017. Great Lakes has ninety days to appeal to the U.S. Supreme Court on Certiorari. In the alternative, it may proceed with its lawsuit against the Foreign Essar Affiliates in the state of Minnesota. Employees Retirement System of the City of St. Louis v. TC PipeLines GP, Inc., et al. – On October 13, 2015, an alleged unitholder of the Partnership filed a class action and derivative complaint in the Delaware Court of Chancery against the General Partner, TransCanada American Investments, Ltd. (TAIL) and TransCanada, and the Partnership as a nominal defendant. The complaint alleges direct and derivative claims for breach of contract, breach of the duty of good faith and fair dealing, aiding and abetting breach of contract, and tortious interference in connection with the 2015 GTN Acquisition, including the issuance by the Partnership of $95 million in Class B Units and amendments to the Partnership Agreement to provide for the issuance of the Class B Units. Plaintiff seeks, among other things, to enjoin future issuances of Class B Units to TransCanada or any of its subsidiaries, disgorgement of certain distributions to the General Partner, TransCanada and any related entities, return of some or all of the Class B Units to the Partnership, rescission of the amendments to the Partnership Agreement, monetary damages and attorney fees. The Partnership has moved to dismiss the complaint and intends to defend vigorously against the claims asserted. In April 2016, the Chancery Court granted the Partnership and other defendants' motion to dismiss the plaintiffs' complaint. The plaintiff has appealed the decision to dismiss its claims. The appeal of this matter was heard by the Delaware Supreme Court in December, 2016. The court found in TransCanada's favor and dismissed the Plaintiff's motion. There are no further rights of appeal.

VARIABLE INTEREST ENTITIES

The entire disclosure for loss and gain contingencies. Describes any existing condition, situation, or set of circumstances involving uncertainty as of the balance sheet date (or prior to issuance of the financial statements) as to a probable or reasonably possible loss incurred by an entity that will ultimately be resolved when one or more future events occur or fail to occur, and typically discloses the amount of loss recorded or a range of possible loss, or an assertion that no reasonable estimate can be made.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14472-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12021-110248

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14394-108349

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12053-110248

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14453-108349

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14615-108349

+ Details

VARIABLE INTEREST ENTITIES

12 Months Ended

Dec. 31, 2016

VARIABLE INTEREST ENTITIES

NOTE 22 VARIABLE INTEREST ENTITIES

In the normal course of business, the Partnership must re-evaluate its legal entities under the newly effective consolidation guidance to determine if those that are considered to be VIEs are appropriately consolidated or if they should be accounted for under other GAAP. A variable interest entity (VIE) is a legal entity that does not have sufficient equity at risk to finance its activities without additional subordinated financial support or is structured such that equity investors lack the ability to make significant decisions relating to the entity's operations through voting rights or do not substantively participate in the gains or losses of the entity. A VIE is appropriately consolidated if the Partnership is considered to be the primary beneficiary. The VIE's primary beneficiary is the entity that has both (1) the power to direct the activities of the VIE that most significantly impact the VIEs economic performance and (2) the obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE.

As a result of its analysis, the Partnership continues to consolidate all legal entities in which it has a variable interest and for which it is considered to be the primary beneficiary. VIEs where the Partnership is not the primary beneficiary, but has a variable interest in the entity, are accounted for as equity investments.

Consolidated VIEs

The Partnership's consolidated VIEs consist of the Partnership's ILPs that hold interests in the Partnership's pipeline systems. After considering the purpose and design of the ILPs and the risks that they were designed to create and pass through to the Partnership, the Partnership has concluded that it is the primary beneficiary of these ILPs because of the significant amount of variability that it absorbs from the ILPs' economic performance.

The assets and liabilities held through these VIEs that are not available to creditors of the Partnership and whose investors have no recourse to the credit of the Partnership are held through GTN, Tuscarora, Northern Border, Great Lakes and PNGTS due to their third party debt. The following table presents the total assets and liabilities of these entities that are included in the Partnership's Consolidated Balance Sheets:

(millions of dollars)		December 31, 2016		December 31, 2015

ASSETS (LIABILITIES)(a)
	Accounts receivable and other	24		21
	Inventories	6		6
	Other current assets	4		4
	Equity investments	1,044		965
	Plant, property and equipment	847		872
	Other assets	2		2
	Accounts payable and accrued liabilities	(20	)	(26	)
	Accounts payable to affiliates, net	(28	)	(6	)
	Accrued interest	(1	)	(1	)
	Current portion of long-term debt	(23	)	(14	)
	Long-term debt	(313	)	(326	)
	Other liabilities	(25	)	(24	)


(a)	North Baja and Bison, which are also assets held through our consolidated VIEs, are excluded as the assets of these entities can be used for purposes other than the settlement of the VIE's obligations.

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2016
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	NOTE 23 SUBSEQUENT EVENTS Management of the Partnership has reviewed subsequent events through February 28, 2017, the date the financial statements were issued, and concluded there were no events or transactions during this period that would require recognition or disclosure in the consolidated financial statements other than what is disclosed here and/or those already disclosed in the preceding notes. On January 23, 2017, the board of directors of our General Partner declared the Partnership's fourth quarter 2016 cash distribution in the amount of $0.94 per common unit and was paid on February 14, 2017 to unitholders of record as of February 2, 2017. The declared distribution totaled $68 million and was paid in the following manner: $64 million to common unitholders (including $5 million to the General Partner as holder of 5,797,106 common units and $11 million to another subsidiary of TransCanada as holder of 11,287,725 common units) and $4 million to our General Partner, which included $2 million for its effective two percent general partner interest and $2 million of IDRs payment. On January 23, 2017, the board of directors of our General Partner declared distributions to Class B unitholders in the amount of $22 million and was paid on February 14, 2017. The Class B distribution represents an amount equal to 30 percent of GTN's distributable cash flow during the year ended December 31, 2016 less $20 million. Northern Border declared its December 2016 distribution of $16 million on January 9, 2017, of which the Partnership received its 50 percent share or $8 million on January 31, 2016. Northern Border declared its January 2017 distribution of $18 million on February 15, 2017, of which the Partnership received its 50 percent share or $9 million on February 28, 2017. Great Lakes declared its fourth quarter 2016 distribution of $14 million on January 9, 2017, of which the Partnership received its 46.45 percent share or $7 million. The distribution was paid on February 1, 2017.

SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2016
SIGNIFICANT ACCOUNTING POLICIES
Basis of Presentation - Consolidation and equity method of accounting	(a) Basis of Presentation The Partnership consolidates its interests on entities over which it is able to exercise control. To the extent there are interests owned by other parties, these interests are included in non-controlling interests. The Partnership uses the equity method of accounting for its investments in entities over which it is able to exercise significant influence.
Basis of Presentation - Transactions between entities under common control	On January 1, 2016, the Partnership acquired a 49.9 percent interest in PNGTS (PNGTS Acquisition) from a subsidiary of TransCanada. The PNGTS Acquisition was accounted for as a transaction between entities under common control, similar to a pooling of interests, whereby the equity investment in PNGTS was recorded at TransCanada's carrying value and the total excess purchase price paid was recorded as a reduction in Partners' Equity. Refer to Note 6 for additional disclosure regarding the PNGTS Acquisition. On April 1, 2015 and October 1, 2014, the Partnership acquired the remaining 30 percent interest in GTN and Bison, respectively, from subsidiaries of TransCanada. These acquisitions resulted in GTN and Bison being wholly-owned by the Partnership. Prior to these transactions, the remaining 30 percent interests held by subsidiaries of TransCanada were reflected as non-controlling interests in the Partnership's consolidated financial statements. The acquisitions of these already-consolidated entities were accounted as a transaction between entities under common control, similar to a pooling of interests, whereby the acquired interests were recorded at TransCanada's carrying value and the total excess purchase price paid was recorded as a reduction in Partners' Equity. Refer to Note 6 for additional disclosures regarding these acquisitions.
Use of Estimates	(b) Use of Estimates The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Although management believes these estimates are reasonable, actual results could differ from these estimates.
Cash and Cash Equivalents	(c) Cash and Cash Equivalents The Partnership's cash and cash equivalents consist of cash and highly liquid short-term investments with original maturities of three months or less and are recorded at cost, which approximates fair value.
Trade Accounts Receivable	(d) Trade Accounts Receivable Trade accounts receivable are recorded at the invoiced amount and do not bear interest. We review our accounts receivable regularly and record allowances for doubtful accounts using the specific identification method.
Natural Gas Imbalances	(e) Natural gas imbalances Natural gas imbalances occur when the actual amount of natural gas delivered to or received from a pipeline system differs from the amount of natural gas scheduled to be delivered or received. The Partnership values these imbalances due to or from shippers and interconnecting parties at current index prices. Imbalances are settled in kind, subject to the terms of the pipelines' tariff. Imbalances due from others are reported as trade accounts receivable or accounts receivable from affiliates under the caption accounts receivable and other on the balance sheets. Imbalances owed to others are reported on the balance sheets as accounts payable and accrued liabilities and accounts payable to affiliates. In addition, the Partnership classifies all imbalances as current as the Partnership expects to settle them within a year.
Inventories	(f) Inventories Inventories primarily consist of materials and supplies and are carried at the lower of weighted average cost or market.
Plant, Property and Equipment	(g) Plant, Property and Equipment Plant, property and equipment are stated at original cost. Costs of restoring the land above and around the pipeline are capitalized to pipeline facilities and depreciated over the remaining life of the related pipeline facilities. Pipeline facilities and compression equipment have an estimated useful life of 20 to 77 years and metering and other equipment ranges from 5 to 77 years. Depreciation is calculated on a straight-line composite basis over the assets' estimated useful lives. Repair and maintenance costs are expensed as incurred. Costs that are considered a betterment are capitalized. The Partnership's subsidiaries capitalize a carrying cost on funds invested in the construction of long lived assets. This carrying cost includes a return on the investment financed by debt and equity allowance for funds used during construction (AFUDC), calculated based the average cost of debt and equity. Capitalized carrying costs for AFUDC debt and equity are reflected as an increase in the cost of plant, property and equipment on the balance sheets. Amounts included in construction work in progress are not amortized until transferred into service.
Impairment of Equity Method Investments	(h) Impairment of Equity Method Investments We review our equity method investments when a significant event or change in circumstances has occurred that may have an adverse effect on the fair value of each investment. When such events or changes occur, we compare the estimated fair value to the carrying value of the related investment. We calculate the estimated fair value of an investment in an equity method investee using an income approach and market approach. The development of fair value estimates requires significant judgment including estimates of future cash flows, which is dependent on internal forecasts, estimates of the long-term rate of growth for the investee, estimates of the useful life over which cash flows will occur, and determination of weighted average cost of capital. The estimates used to calculate the fair value of an investee can change from year to year based on operating results and market conditions. Changes in these estimates and assumptions could materially affect the determination of fair value and our assessment as to whether an investment in an equity method investee has suffered an impairment. If the estimated fair value of an investment is less than its carrying value, we are required to determine if the decline in fair value is other than temporary. This determination considers the aforementioned valuation methodologies, the length of time and the extent to which fair value has been less than carrying value, the financial condition and near-term prospects of the investee, including any specific events which may influence the operations of the investee, the intent and ability of the holder to retain its investment in the investee for a period of time sufficient to allow for any anticipated recovery in market value, and other facts and circumstances. If the fair value of an investment is less than its carrying value and the decline in value is determined to be other than temporary, we record an impairment charge.
Impairment of Long-lived Assets	(i) Impairment of Long-lived Assets The Partnership reviews long-lived assets, such as plant, property and equipment for impairment whenever events or changes in circumstances indicate the carrying value may not be recoverable. If the total of the estimated undiscounted future cash flows is less than the carrying value of the assets, an impairment loss is recognized for the excess of the carrying value over the fair value of the assets.
Partners' Equity	(j) Partners' Equity Costs incurred in connection with the issuance of units are deducted from the proceeds received.
Revenue Recognition	(k) Revenue Recognition Transmission revenues are recognized in the period in which the service is provided. When a rate case is pending final FERC approval, a portion of the revenue collected is subject to possible refund. As of December 31, 2016, 2015 and 2014, the Partnership has not recognized any transmission revenue that is subject to possible refund.
Income Taxes	(l) Income Taxes The Partnership is not subject to federal or state income tax. The tax effect of the Partnership's activities accrues to its partners. The Partnership's taxable income or loss, which may vary substantially from the net income or loss reported in the consolidated statement of income, is includable in the federal income tax returns of each partner. The aggregate difference in the basis of the Partnership's net assets for financial and income tax purposes cannot be readily determined because all information regarding each partner's tax attributes related to the partnership is not available.
Acquisitions and Goodwill	(m) Acquisitions and Goodwill The Partnership accounts for business acquisitions from third parties using the acquisition method of accounting and, accordingly, the assets and liabilities of the acquired entities are recorded at their estimated fair values at the date of acquisition. The excess of the purchase price over the fair value of net assets acquired is attributed to goodwill. Goodwill is not amortized and is tested on an annual basis for impairment or more frequently if any indicators of impairment are evident. The Partnership initially assesses qualitative factors to determine whether events or changes in circumstances indicate that the goodwill might be impaired. If the Partnership does not conclude that it is more likely than not that fair value of the reporting unit is greater than its carrying value, the first step of the two-step impairment test is performed by comparing the fair value of the reporting unit to its book value, which includes goodwill. If the fair value is less than book value, an impairment is indicated and a second step is performed to measure the amount of the impairment. In the second step, the implied fair value of goodwill is calculated by deducting the recognized amounts of all tangible and intangible net assets of the reporting unit from the fair value determined in the initial assessment. If the carrying value of goodwill exceeds the calculated implied fair value of goodwill, an impairment charge is recorded. At December 31, 2016 and 2015, we had $130 million of goodwill recorded on our consolidated balance sheet related to the North Baja ($48 million) and Tuscarora ($82 million) acquisitions. No impairment of goodwill existed at December 31, 2016 (Refer also to Note 20). The Partnership accounts for business acquisitions between itself and TransCanada, also known as "dropdowns", as transactions between entities under common control. Using this approach, the assets and liabilities of the acquired entities are recorded at TransCanada's carrying value. In the event recasting is required, the Partnership's historical financial information will be recast, except net income (loss) per common unit, to include the acquired entities for all periods presented. If the fair market value paid for the acquired entities is greater than the recorded net assets of the acquired entities, the excess purchase price paid is recorded as a reduction in Partners' Equity. Similarly, if the fair market value paid for the acquired entities is less than the recorded net assets of the acquired entities, the excess of assets acquired is recorded as an increase in Partners' Equity.
Fair Value Measurements	(n) Fair Value Measurements For cash and cash equivalents, receivables, accounts payable, certain accrued expenses and short-term debt, the carrying amount approximates fair value due to the short maturities of these instruments. For long-term debt instruments and the interest rate swap agreements, fair value is estimated based upon market values (if applicable) or on the current interest rates available to us for debt with similar terms and remaining maturities. Considerable judgment is required in developing these estimates.
Derivative Financial Instruments and Hedging Activities	(o) Derivative Financial Instruments and Hedging Activities The Partnership recognizes all derivative instruments as either assets or liabilities in the balance sheet at their respective fair values. For derivatives designated in hedging relationships, changes in the fair value are either offset through earnings against the change in fair value of the hedged item attributable to the risk being hedged or recognized in accumulated other comprehensive income, to the extent the derivative is effective at offsetting the changes in cash flows being hedged until the hedged item affects earnings. The Partnership only enters into derivative contracts that it intends to designate as a hedge of a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (cash flow hedge). For all hedging relationships, the Partnership formally documents the hedging relationship and its risk management objective and strategy for undertaking the hedge, the hedging instrument, the hedged transaction, the nature of the risk being hedged, how the hedging instrument's effectiveness in offsetting the hedged risk will be assessed prospectively and retrospectively, and a description of the method used to measure ineffectiveness. The Partnership also formally assesses, both at the inception of the hedging relationship and on an ongoing basis, whether the derivatives that are used in hedging relationships are highly effective in offsetting changes in cash flows of hedged transactions. For derivative instruments that are designated and qualify as part of a cash flow hedging relationship, the effective portion of the gain or loss on the derivative is reported as a component of other comprehensive income and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. Gains and losses on the derivative representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized in current earnings. The Partnership discontinues hedge accounting prospectively when it determines that the derivative is no longer effective in offsetting cash flows attributable to the hedged risk, the derivative expires or is sold, terminated, or exercised, the cash flow hedge is de-designated because a forecasted transaction is not probable of occurring, or management determines to remove the designation of the cash flow hedge. In all situations in which hedge accounting is discontinued and the derivative remains outstanding, the Partnership continues to carry the derivative at its fair value on the balance sheet and recognizes any subsequent changes in its fair value in earnings. When it is probable that a forecasted transaction will not occur, the Partnership discontinues hedge accounting and recognizes immediately in earnings gains and losses that were accumulated in other comprehensive income related to the hedging relationship.
Asset Retirement Obligation	(p) Asset Retirement Obligation The Partnership recognizes the fair value of a liability for asset retirement obligations in the period in which it is incurred, when a legal obligation exists and a reasonable estimate of fair value can be made. The fair value is added to the carrying amount of the associated asset and the liability is accreted through charges to operating expenses. The Partnership has determined it has legal obligations associated with its natural gas pipelines and related transmission facilities. The obligations relate primarily to purging and sealing the pipelines if they are abandoned. The Partnership is also required to operate and maintain its natural gas pipeline system, and intends to do so as long as supply and demand for natural gas exists, which the Partnership expects for the foreseeable future. Therefore, the Partnership believes its natural gas pipeline system assets have indeterminate lives and, accordingly, has recorded no asset retirement obligation as of December 31, 2016 and 2015.
Government Regulation	(q) Government Regulation The Partnership's subsidiaries are subject to regulation by FERC. Under regulatory accounting principles, certain assets or liabilities that result from the regulated ratemaking process may be recorded that would not be recorded under GAAP for non-regulated entities. The timing of recognition of certain revenues and expenses in our regulated business may differ from that otherwise expected under GAAP to appropriately reflect the economic impact of the regulators' decisions regarding revenues and rates. The Partnership regularly evaluates the continued applicability of regulatory accounting, considering such factors as regulatory changes, the impact of competition, and the ability to recover regulatory assets. At December 31, 2016, the Partnership had regulatory assets amounting to $1 million reported as part of other current assets in the balance sheet representing volumetric fuel tracker assets that are settled with in-kind exchanges with customers continually (2015 – $2 million). Regulatory liabilities are included in other long-term liabilities (refer to Note 8). AFUDC is capitalized and included in plant, property and equipment.
Debt Issuance Costs	(r) Debt Issuance Costs Costs related to the issuance of debt are deferred and amortized using the effective interest rate method over the term of the related debt. Refer also to Note 3 – Imputation of Interest for the change in accounting policy related to debt issuance costs.

ORGANIZATION (Tables)

12 Months Ended

Dec. 31, 2016

ORGANIZATION

Schedule of ownership interests in natural gas pipeline systems

Pipeline	Length	Description	Ownership

Gas Transmission Northwest LLC (GTN)	1,377 miles	Extends between an interconnection near Kingsgate, British Columbia, Canada at the Canadian border to a point near Malin, Oregon at the California border and delivers natural gas to the Pacific Northwest and to California.	100 percent
Bison Pipeline LLC (Bison)	303 miles	Extends from a location near Gillette, Wyoming to Northern Border's pipeline system in North Dakota. Bison can transport natural gas from the Powder River Basin to Midwest markets.	100 percent
North Baja Pipeline, LLC (North Baja)	86 miles	Extends between an interconnection with the El Paso Natural Gas Company pipeline near Ehrenberg, Arizona and an interconnection with a natural gas pipeline near Ogilby, California on the Mexican border transporting natural gas in the southwest. North Baja is a bi-directional pipeline.	100 percent
Tuscarora Gas Transmission Company (Tuscarora)	305 miles	Extends between the GTN pipeline near Malin, Oregon to its terminus near Reno, Nevada and delivers natural gas in northeastern California and northwestern Nevada.	100 percent
Northern Border Pipeline Company (Northern Border)	1,412 miles	Extends between the Canadian border near Port of Morgan, Montana to a terminus near North Hayden, Indiana, south of Chicago. Northern Border is capable of receiving natural gas from Canada, the Williston Basin and Rocky Mountain area for deliveries to the Midwest. ONEOK Partners, L.P. owns the remaining 50 percent of Northern Border.	50 percent
Portland Natural Gas Transmission System (PNGTS)	295 miles	Connects with the TransQuebec and Maritimes Pipeline (TQM) at the Canadian border to deliver natural gas to customers in the U.S. northeast. TransCanada owns 11.81 percent of PNGTS. Northern New England Investment Company, Inc. owns the remaining 38.29 percent of PNGTS.	49.9 percent
Great Lakes Gas Transmission Limited Partnership (Great Lakes)	2,115 miles	Connects with the TransCanada Mainline at the Canadian border near Emerson, Manitoba, Canada and St. Clair, Michigan, near Detroit. Great Lakes is a bi-directional pipeline that can receive and deliver natural gas at multiple points along its system. TransCanada owns the remaining 53.55 percent of Great Lakes.	46.45 percent

EQUITY INVESTMENTS (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of equity investments and summarized financial information for equity investees

		Equity Earnings from Unconsolidated Affiliates(b)			Investment in Unconsolidated Affiliates
		Year ended December 31			December 31
	Ownership Interest at December 31, 2016	Year ended December 31			December 31
(millions of dollars)	Ownership Interest at December 31, 2016	2016	2015	2014	2016	2015

Northern Border(a)	50.00%	69	66	69	444	480
Great Lakes	46.45%	28	31	19	474	485 (c)
PNGTS(d)	49.90%	19	–	–	126	–

		116	97	88	1,044	965


(a)	Equity earnings from Northern Border is net of the 12-year amortization of a $10 million transaction fee paid to the operator of Northern Border at the time of the Partnership's additional 20 percent acquisition in April 2006.
(b)	Equity Earnings represents our share in investee's earnings and does not include any impairment charge on the equity method investment recorded as a reduction of carrying value of these investments. Accordingly, no impairment charge was recorded by the Partnership on its equity investees for all the periods presented here except the impairment recognized in 2015 on our investment in Great Lakes as discussed below.
(c)	During the fourth quarter of 2015, we recognized an impairment charge on our investment in Great Lakes amounting to $199 million. See discussion below.
(d)	On January 1, 2016, the Partnership acquired a 49.9 percent interest in PNGTS (Refer to Note 6). For the year ended December 31, 2016, the Partnership recorded no undistributed earnings from PNGTS.

Northern Border

Schedule of equity investments and summarized financial information for equity investees

December 31 (millions of dollars)		2016		2015

Assets
Cash and cash equivalents		14		27
Other current assets		36		33
Plant, property and equipment, net		1,089		1,124
Other assets(a)		14		16

		1,153		1,200

Liabilities and Partners' Equity
Current liabilities		38		39
Deferred credits and other		28		26
Long-term debt, net(a),(b)		430		409
Partners' equity
	Partners' capital	659		728
	Accumulated other comprehensive loss	(2	)	(2	)

		1,153		1,200


(a)	As a result of the application of ASU No. 2015-03 and similar to the presentation of debt discounts, debt issuance costs of $2 million at December 31, 2015 previously reported as other assets in the balance sheet were reclassified as an offset against their respective debt liabilities.
(b)	Includes current maturities of $100 million senior notes at December 31, 2015. During August 2016, the $100 million senior notes were refinanced with a draw on Northern Border's $200 million revolving credit agreement that expires in 2020.

Year ended December 31 (millions of dollars)	2016		2015		2014

Transmission revenues	292		286		293
Operating expenses	(72	)	(70	)	(72	)
Depreciation	(59	)	(60	)	(59	)
Financial charges and other	(21	)	(22	)	(22	)

Net income	140		134		140

Great Lakes

Schedule of equity investments and summarized financial information for equity investees

December 31 (millions of dollars)	2016	2015

Assets
Current assets	66	86
Plant, property and equipment, net	714	727

	780	813

Liabilities and Partners' Equity
Current liabilities	40	31
Long-term debt, net(a),(b)	278	297
Partners' equity	462	485

	780	813


(a)	The application of ASU No. 2015-03 did not have a material effect on Great Lakes' financial statements.
(b)	Includes current maturities of $19 million as of December 31, 2016 (December 31, 2015 – $19 million).

Year ended December 31 (millions of dollars)	2016		2015		2014

Transmission revenues	179		177		146
Operating expenses	(69	)	(59	)	(53)
Depreciation	(28	)	(28	)	(28)
Financial charges and other	(21	)	(23	)	(25)

Net income	61		67		40

PLANT, PROPERTY AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2016

PLANT, PROPERTY AND EQUIPMENT

Schedule of plant, property and equipment

	2016				2015
December 31 (millions of dollars)	Cost	Accumulated Depreciation		Net Book Value	Cost	Accumulated Depreciation		Net Book Value

Pipeline	2,091	(701	)	1,390	2,086	(638	)	1,448
Compression	519	(148	)	371	516	(134	)	382
Metering and other	159	(43	)	116	156	(39	)	117
Construction in progress	4	–		4	2	–		2

	2,773	(892	)	1,881	2,760	(811	)	1,949

ACQUISITIONS (Tables)

12 Months Ended

Dec. 31, 2016

Portland Natural Gas Transmission System

Schedule of purchase price

(millions of dollars)

Net Purchase Price(a)		193
Less: TransCanada's carrying value of PNGTS' net assets at January 1, 2016		120

Excess purchase price(b)		73


(a)	Total purchase price of $228 million less the assumption of $35 million of proportional PNGTS debt by the Partnership.
(b)	The excess purchase price of $73 million was recorded as a reduction in Partners' Equity.

GTN

Schedule of purchase price

(millions of dollars)

Net Purchase Price(a)		359
Less: TransCanada's carrying value of non-controlling interest at April 1, 2015		232

Excess purchase price(b)		127


(a)	Total purchase price of $457 million less the assumption of $98 million of proportional GTN debt by the Partnership.
(b)	The excess purchase price of $127 million was recorded as a reduction in Partners' Equity.

Bison

Schedule of purchase price

(millions of dollars)

Total cash consideration		217
TransCanada's carrying value of non-controlling interest at October 1, 2014		188

Excess purchase price		29

DEBT AND CREDIT FACILITIES (Tables)

12 Months Ended

Dec. 31, 2016

DEBT AND CREDIT FACILITIES

Schedule of debt and credit facilities

(unaudited) (millions of dollars)		December 31, 2016	Weighted Average Interest Rate for the Year Ended December 31, 2016		December 31, 2015	Weighted Average Interest Rate for the Year Ended December 31, 2015

TC PipeLines, LP
	Senior Credit Facility due 2021	160	1.72%		200	1.44%
	2013 Term Loan Facility due 2018	500	1.73%		500	1.44%
	2015 Term Loan Facility due 2018	170	1.63%		170	1.47%
	4.65% Unsecured Senior Notes due 2021	350	4.65%	(b)	350	4.65%	(b)
	4.375% Unsecured Senior Notes due 2025	350	4.375%	(b)	350	4.375%	(b)
GTN
	5.29% Unsecured Senior Notes due 2020	100	5.29%	(b)	100	5.29%	(b)
	5.69% Unsecured Senior Notes due 2035	150	5.69%	(b)	150	5.69%	(b)
	Unsecured Term Loan Facility due 2019	65	1.43%		75	1.15%
Tuscarora
	Unsecured Term Loan due 2019	10	1.64%		–	–
	3.82% Series D Senior Notes due 2017	12	3.82%	(b)	16	3.82%	(b)

		1,867			1,911
Less: unamortized debt issuance costs and debt discount(a)		9			8
Less: current portion		23			14

		1,835			1,889


(a)	As a result of the application of ASU No. 2015-03 and similar to the presentation of debt discounts, debt issuance costs of $7 million at December 31, 2015 previously reported as other assets in the balance sheet were reclassified as an offset against debt. Refer to Note 3, Accounting Pronouncements.
(b)	Fixed interest rate.

Schedule of principal repayments required on debt

(millions of dollars)

2017		23
2018		691
2019		43
2020		100
2021		510
Thereafter		500

		1,867

OTHER LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2016

OTHER LIABILITIES

Schedule of other liabilities

December 31 (millions of dollars)	2016	2015

Regulatory liabilities	25	24
Other liabilities	3	3

	28	27

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)

12 Months Ended

Dec. 31, 2016

ACCUMULATED OTHER COMPREHENSIVE LOSS

Schedule of changes in accumulated other comprehensive loss (AOCL) by components

(millions of dollars)		Cash flow hedges

Balance at December 31, 2013		(1)
Other comprehensive loss before reclassifications		(1)
Amounts reclassified from AOCL		–

Net other comprehensive loss		(1)

Balance at December 31, 2014		(2)
Other comprehensive loss before reclassifications		–
Amounts reclassified from AOCL		–

Net other comprehensive loss		–

Balance at December 31, 2015		(2)
Other comprehensive income before reclassifications		3
Amounts reclassified from AOCL		(1)

Net other comprehensive loss		2

Balance as of December 31, 2016		–

FINANCIAL CHARGES AND OTHER (Tables)

12 Months Ended

Dec. 31, 2016

FINANCIAL CHARGES AND OTHER

Schedule of components of financial charges and other

Year ended December 31 (millions of dollars)	2016		2015		2014

Interest expense(a)	65		59		49
Net realized loss related to the interest rate swaps	3		2		2
Other	(1	)	(5	)	(1	)

	67		56		50


(a)	Effective January 1, 2016, interest expense includes amortization of debt issuance costs and discount costs. Refer to Note 3.

NET INCOME (LOSS) PER COMMON UNIT (Tables)

12 Months Ended

Dec. 31, 2016

NET INCOME (LOSS) PER COMMON UNIT

Schedule of net income (loss) per common unit

(millions of dollars, except per common unit amounts)	2016		2015		2014

Net income attributable to controlling interests	244		13		172
Net income attributable to General Partner	(4	)	–		(3	)
Incentive distributions attributable to the General Partner(a)	(7	)	(3	)	(1	)
Net income attributable to the Class B units(b)	(22	)	(12	)	–

Net income (loss) attributable to common units	211		(2	)	168

Weighted average common units outstanding (millions) – basic and diluted	65.7	(c)	63.9		62.7
Net income (loss) per common unit – basic and diluted	$ 3.21		$ (0.03	)	$ 2.67


(a)	Under the terms of the Partnership Agreement, for any quarterly period, the participation of the incentive distribution rights (IDRs) is limited to the available cash distributions declared. Accordingly, incentive distributions allocated to the General Partner are based on the Partnership's available cash during the current reporting period, but declared and paid in the subsequent reporting period.
(b)	As discussed in Note 9, the Class B units entitle TransCanada to a distribution which is an amount based on 30 percent of GTN's distributions after exceeding certain annual thresholds. The distribution will be payable in the first quarter with respect to the prior year's distributions. Consistent with the application of Accounting Standards Codification (ASC) Topic 260 – "Earnings per share", the Partnership allocated a portion of net income attributable to controlling interests to the Class B units in an amount equal to 30 percent of GTN's total distributable cash flows during the year ended December 31, 2016 less the threshold level of $20 million (2015 – less $15 million). During the year ended December 31, 2016, 30 percent of GTN's total distributable cash flow was $42 million. As a result of exceeding the threshold level of $20 million, $22 million of net income attributable to controlling interests was allocated to the Class B units at December 31, 2016 (2015 – $12 million). Refer to Note 9.
(c)	Includes the common units subject to rescission. These units are treated as outstanding for financial reporting purposes. Refer to Note 9.

CASH DISTRIBUTIONS (Tables)

12 Months Ended

Dec. 31, 2016

CASH DISTRIBUTIONS

Schedule of allocations of available cash from operating surplus between common unitholders and General Partner

		Marginal Percentage Interest in Distribution
	Total Quarterly Distribution Per Unit Target Amount	Common Unitholders	General Partner

Minimum Quarterly Distribution	$0.45	98%	2%
First Target Distribution	above $0.45 up to $0.81	98%	2%
Second Target Distribution	above $0.81 up to $0.88	85%	15%
Thereafter	above $0.88	75%	25%

Schedule of distributions

					Limited Partners			General Partner
Declaration Date		Payment Date		Per Unit Distribution	Common Units	Class B Units(c)		2%	IDRs(a)	Total Cash Distribution

1/16/2014		2/14/2014		$ 0.81	$ 50	$ –		$ 1	$–	$ 51
4/25/2014		5/15/2014		$ 0.81	$ 51	$ –		$ 1	$–	$ 52
7/23/2014		8/14/2014		$ 0.84	$ 53	$ –		$ 1	$–	$ 54
10/23/2014		11/14/2014		$ 0.84	$ 53	$ –		$ 1	$ 1	$ 55
1/22/2015		2/13/2015		$ 0.84	$ 54	$ –		$ 1	$–	$ 55
4/23/2015		5/15/2015		$ 0.84	$ 54	$ –		$ 1	$–	$ 55
7/23/2015		8/14/2015		$ 0.89	$ 56	$ –		$ 2	$ 1	$ 59
10/22/2015		11/13/2015		$ 0.89	$ 57	$ –		$ 1	$ 1	$ 59
1/21/2016		2/12/2016		$ 0.89	$ 57	$ 12	(d)	$ 1	$ 1	$ 71
4/21/2016		5/13/2016		$ 0.89	$ 58	$ –		$ 1	$ 1	$ 60
7/21/2016		8/12/2016		$ 0.94	$ 62	$ –		$ 1	$ 2	$ 65
10/20/2016		11/14/2016		$ 0.94	$ 63	$ –		$ 1	$ 2	$ 66
1/23/2017	(b)	2/14/2017	(b)	$ 0.94	$ 64	$ 22	(e)	$ 2	$ 2	$ 90


(a)	The distributions paid for the year ended December 31, 2016 included incentive distributions to the General Partner of $6 million (2015 – $2 million, 2014 – $1 million).
(b)	On February 14, 2017, we paid a cash distribution of $0.94 per unit on our outstanding common units to unitholders of record at the close of business on February 2, 2017 (refer to Note 23).
(c)	The Class B units issued by us on April 1, 2015 represent limited partner interests in us and entitle TransCanada to an annual distribution which is an amount based on 30 percent of GTN's annual distributions after exceeding certain annual thresholds (refer to Note 6 and 9).
(d)	On February 12, 2016, we paid TransCanada $12 million representing 30 percent of GTN's total distributable cash flows for the nine months ended December 31, 2015 less $15 million.
(e)	On February 14, 2017, we paid TransCanada $22 million representing 30 percent of GTN's total distributable cash flows for the year ended December 31, 2016 less $20 million (refer to Note 9 and 23).

CHANGE IN OPERATING WORKING CAPITAL (Tables)

12 Months Ended

Dec. 31, 2016

CHANGE IN OPERATING WORKING CAPITAL

Schedule of change in operating working capital

Year Ended December 31 (millions of dollars)	2016		2015		2014

Change in accounts receivable and other	(3	)	(1	)	1
Change in other current assets	(3	)	1		1
Change in accounts payable and accrued liabilities(a)	5		(3	)	4
Change in accounts payable to affiliates	2		(10)	(b)	11
Change in accrued interest	1		4		–

Change in operating working capital	2		(9	)	17


(a)	The accrual of $10 million for the construction of GTN's Carty Lateral in December 31, 2015 was paid during the first quarter 2016. Accordingly, the payment was reported as capital expenditures in our cash flow statement during 2016.
(b)	Excludes certain non-cash items primarily related to accruals of $10 million for construction of GTN's Carty Lateral and $2 million of costs related to acquisition of 49.9 percent interest in PNGTS (Refer to Note 6).

TRANSACTIONS WITH MAJOR CUSTOMERS (Tables)

12 Months Ended

Dec. 31, 2016

TRANSACTIONS WITH MAJOR CUSTOMERS

Schedule of revenues from major customers

Year Ended December 31 (millions of dollars)	2016	2015	2014

Anadarko Energy Services Company (Anadarko)	48	48	48
Pacific Gas and Electric Company (Pacific Gas)	36	42	45

RELATED PARTY TRANSACTIONS (Tables)

12 Months Ended

Dec. 31, 2016

RELATED PARTY TRANSACTIONS

Summary of capital and operating costs charged to pipeline systems by related party

Year ended December 31 (millions of dollars)		2016	2015	2014

Capital and operating costs charged by TransCanada's subsidiaries to:
	Great Lakes(a)	30	30	30
	Northern Border(a)	32	36	35
	PNGTS(a)(b)	8	–	–
	GTN(a)(c)	27	30	30
	Bison(a)(d)	2	4	6
	North Baja	4	5	5
	Tuscarora	5	4	4
Impact on the Partnership's net income attributable to controlling interests:
	Great Lakes	13	13	13
	Northern Border	12	14	16
	PNGTS(b)	4	–	–
	GTN(c)	24	25	19
	Bison(d)	3	4	4
	North Baja	4	5	4
	Tuscarora	4	4	4

Summary of amount payable to related party for costs charged

December 31 (millions of dollars)		2016	2015

Amount payable to TransCanada's subsidiaries for costs charged in the year by:
	Great Lakes(a)	4	3
	Northern Border(a)	4	5
	PNGTS(a)	1	–
	GTN	3	3
	Bison	1	–
	North Baja	1	–
	Tuscarora	1	1


(a)	Represents 100 percent of the costs.
(b)	In 2016, the Partnership acquired a 49.9 percent interest in PNGTS (Refer to Note 6).
(c)	In 2015, the Partnership acquired the remaining 30 percent interest in GTN (Refer to Note 6).
(d)	In 2014, the Partnership acquired the remaining 30 percent interest in Bison (Refer to Note 6).

QUARTERLY FINANCIAL DATA (unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

QUARTERLY FINANCIAL DATA (unaudited)

Schedule of selected unaudited financial data

Quarter ended (millions of dollars except per common unit amounts)	Mar 31	Jun 30	Sept 30	Dec 31

2016
Transmission revenues	86	89	91	91
Equity earnings(a)(c)	42	22	24	28
Net income	73	54	58	60
Net income attributable to controlling interests	73	54	58	60
Net income per common unit	$ 1.10	$ 0.76	$ 0.65	$ 0.70
Cash distribution paid	71	60	65	66

2015
Transmission revenues	87	85	83	89
Equity earnings(a)	31	15	17	34
Impairment of equity-method investment(b)	–	–	–	(199	)
Net income (loss)	64	44	49	(137	)
Net income (loss) attributable to controlling interests	57	44	49	(137	)
Net income (loss) per common unit	$ 0.88	$ 0.66	$ 0.70	$ (2.24	)
Cash distribution paid	55	55	59	59


(a)	Equity Earnings represents our share in investee's earnings and does not include any impairment charge on equity method goodwill included as part of the carrying value of our equity investments.
(b)	During the three months ended December 31, 2015, we recognized an impairment charge on our investment in Great Lakes amounting to $199 million. During the year ended December 31, 2015, no impairment has been identified on our investment in Northern Border (Refer to Note 4).
(c)	During the year ended December 31, 2016, no impairment has been identified related to our equity investments in Northern Border, Great Lakes or PNGTS.

ACCOUNTS RECEIVABLE AND OTHER (Tables)

12 Months Ended

Dec. 31, 2016

ACCOUNTS RECEIVABLE AND OTHER

Schedule of accounts receivable and other

December 31 (millions of dollars)	2016	2015

Trade accounts receivable, net of allowance of nil	34	32
Imbalance receivable from affiliates	2	1
Other	1	–

	37	33

VARIABLE INTEREST ENTITIES (Tables)

12 Months Ended

Dec. 31, 2016

VARIABLE INTEREST ENTITIES

Schedule of assets and liabilities held through VIEs whose assets cannot be used for purposes other settlement of their obligations

(millions of dollars)		December 31, 2016		December 31, 2015

ASSETS (LIABILITIES)(a)
	Accounts receivable and other	24		21
	Inventories	6		6
	Other current assets	4		4
	Equity investments	1,044		965
	Plant, property and equipment	847		872
	Other assets	2		2
	Accounts payable and accrued liabilities	(20	)	(26	)
	Accounts payable to affiliates, net	(28	)	(6	)
	Accrued interest	(1	)	(1	)
	Current portion of long-term debt	(23	)	(14	)
	Long-term debt	(313	)	(326	)
	Other liabilities	(25	)	(24	)


(a)	North Baja and Bison, which are also assets held through our consolidated VIEs, are excluded as the assets of these entities can be used for purposes other than the settlement of the VIE's obligations.

Tabular disclosure of the significant judgments and assumptions made in determining whether a variable interest (as defined) held by the entity requires the variable interest entity (VIE) (as defined) to be consolidated and (or) disclose information about its involvement with the VIE, individually or in aggregate (as applicable); the nature of restrictions, if any, on the consolidated VIE's assets and on the settlement of its liabilities reported by an entity in its statement of financial position, including the carrying amounts of such assets and liabilities; the nature of, and changes in, the risks associated with involvement in the VIE; how involvement with the VIE affects the entity's financial position, financial performance, and cash flows; the lack of recourse if creditors (or beneficial interest holders) of the consolidated VIE have no recourse to the general credit of the primary beneficiary (if applicable); the terms of arrangements, giving consideration to both explicit arrangements and implicit variable interests, if any, that could require the entity to provide financial support to the VIE, including events or circumstances that could expose the entity to a loss; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; the significant factors considered and judgments made in determining that the power to direct the activities of a VIE that most significantly impact the VIE's economic performance are shared (as defined); the carrying amounts and classification of assets and liabilities of the VIE included in the statement of financial position; the entity's maximum exposure to loss, if any, as a result of its involvement with the VIE, including how the maximum exposure is determined and significant sources of the entity's exposure to the VIE; a comparison of the carrying amounts of the assets and liabilities and the entity's maximum exposure to loss; information about any liquidity arrangements, guarantees, and (or) other commitments by third parties that may affect the fair value or risk of the entity's variable interest in the VIE; whether or not the entity has provided financial support or other support (explicitly or implicitly) to the VIE that it was not previously contractually required to provide or whether the entity intends to provide that support, including the type and amount of the support and the primary reasons for providing the support; and supplemental information the entity determines necessary to provide.

+ References + Details

ORGANIZATION - Ownership Interests in Natural Gas Pipeline Systems (Details)	12 Months Ended
	Dec. 31, 2016 LimitedPartnership mi	Jan. 01, 2016	Dec. 31, 2015	Mar. 31, 2015	Sep. 30, 2014
Organization
Number of intermediate limited partnerships through which pipeline assets are owned \| LimitedPartnership	3
Northern Border
Organization
Remaining ownership interest (as a percent)	50.00%
Interest acquired (as a percent)	50.00%
Great Lakes
Organization
Interest acquired (as a percent)	46.45%		46.45%	46.45%
Portland Natural Gas Transmission System
Organization
Interest acquired (as a percent)	49.90%	49.90%
TransCanada \| GTN
Organization
Remaining noncontrolling ownership interest (as a percent)				30.00%
TransCanada \| Bison
Organization
Remaining noncontrolling ownership interest (as a percent)					30.00%
TransCanada \| Portland Natural Gas Transmission System
Organization
Remaining noncontrolling ownership interest (as a percent)	11.81%
North New England Investment \| Portland Natural Gas Transmission System
Organization
Remaining noncontrolling ownership interest (as a percent)	38.29%
GTN
Organization
Length of pipeline owned (in miles)	1,377
Remaining ownership interest (as a percent)	100.00%
Northern Border
Organization
Length of pipeline owned (in miles)	1,412
Ownership interest (as a percent)	50.00%
Bison
Organization
Length of pipeline owned (in miles)	303
Remaining ownership interest (as a percent)	100.00%
Great Lakes
Organization
Length of pipeline owned (in miles)	2,115
Ownership interest (as a percent)	46.45%
Great Lakes \| TransCanada
Organization
Remaining noncontrolling ownership interest (as a percent)	53.55%
North Baja Pipeline, LLC
Organization
Length of pipeline owned (in miles)	86
Ownership interest (as a percent)	100.00%
Tuscarora Gas Transmission Company
Organization
Length of pipeline owned (in miles)	305
Ownership interest (as a percent)	100.00%
Portland Natural Gas Transmission System
Organization
Length of pipeline owned (in miles)	295
Ownership interest (as a percent)	49.90%
TransCanada \| Great Lakes
Organization
Remaining ownership interest (as a percent)	53.55%
ONEOK Partners, L.P. \| Northern Border
Organization
Remaining ownership interest (as a percent)	50.00%

ORGANIZATION - Capitalization (Details) - shares		12 Months Ended
ORGANIZATION - Capitalization (Details) - shares	Apr. 01, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common units
Partners' Equity
Number of units		67,400,000	64,300,000	63,600,000
General Partner \| TC PipeLines GP, Inc.
Partners' Equity
IDRs ownership (as a percent)		100.00%
Ownership interest in the Partnership (as a percent)	2.00%	2.00%	2.00%	2.00%
Limited Partners \| Common units
Partners' Equity
Number of units		67,454,831
Limited Partners \| Common units \| TC PipeLines GP, Inc.
Partners' Equity
Number of units		5,797,106
Limited Partners \| Common units \| TransCanada
Partners' Equity
Number of units		11,287,725
Limited partner interest (as a percent)		25.30%
Limited Partners \| Class B units \| TransCanada
Partners' Equity
Number of units		1,900,000
Limited partner interest (as a percent)		100.00%

SIGNIFICANT ACCOUNTING POLICIES - Ownership Interests Acquired (Details)	Dec. 31, 2016	Jan. 01, 2016	Apr. 01, 2015	Mar. 31, 2015	Oct. 01, 2014	Sep. 30, 2014
Former parent, TransCanada subsidiaries \| Portland Natural Gas Transmission System \| Transaction between entities under common control
Acquisitions
Interest acquired (as a percent)		49.90%
TransCanada \| Portland Natural Gas Transmission System
Acquisitions
Remaining noncontrolling ownership interest (as a percent)	11.81%
TransCanada \| GTN
Acquisitions
Remaining noncontrolling ownership interest (as a percent)				30.00%
TransCanada \| Bison
Acquisitions
Remaining noncontrolling ownership interest (as a percent)						30.00%
GTN \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control
Acquisitions
Interest acquired (as a percent)			30.00%
Bison \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control
Acquisitions
Interest acquired (as a percent)	30.00%		30.00%		30.00%

SIGNIFICANT ACCOUNTING POLICIES - Useful Lives of Plant, Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2016
Pipeline facilities and compression equipment \| Minimum
PLANT, PROPERTY AND EQUIPMENT
Estimated useful lives	20 years
Pipeline facilities and compression equipment \| Maximum
PLANT, PROPERTY AND EQUIPMENT
Estimated useful lives	77 years
Metering and other equipment \| Minimum
PLANT, PROPERTY AND EQUIPMENT
Estimated useful lives	5 years
Metering and other equipment \| Maximum
PLANT, PROPERTY AND EQUIPMENT
Estimated useful lives	77 years

SIGNIFICANT ACCOUNTING POLICIES - Impairment of Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
EQUITY INVESTMENTS
Impairment of equity-method investment	$ 199		$ 199
Nonrecurring fair value measurement
EQUITY INVESTMENTS
Impairment of equity-method investment		$ 0	0	$ 0
Great Lakes \| Nonrecurring fair value measurement
EQUITY INVESTMENTS
Impairment of equity-method investment	$ 199		$ 199

SIGNIFICANT ACCOUNTING POLICIES - Acquisitions and Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Acquisitions and Goodwill
Goodwill	$ 130	$ 130
Impairment of goodwill	0
North Baja Pipeline, LLC
Acquisitions and Goodwill
Goodwill	48	48
Tuscarora Gas Transmission Company
Acquisitions and Goodwill
Goodwill	$ 82	$ 82

SIGNIFICANT ACCOUNTING POLICIES - Asset Retirement Obligation and Regulatory Assets (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable and other
Regulatory assets and liabilities
Regulatory assets	$ 1,000,000	$ 2,000,000
Pipeline
Asset Retirement Obligation
Asset retirement liabilities	$ 0	$ 0

ACCOUNTING PRONOUNCEMENTS - Imputation of Interest (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
ACCOUNTING PRONOUNCEMENTS
Other assets	$ 1	$ 1
Long-term debt	$ 1,835	1,889
ASU 2015-03, Interest - Imputation of Interest \| Adjustment
ACCOUNTING PRONOUNCEMENTS
Other assets		(7)
Long-term debt		$ (7)

ACCOUNTING PRONOUNCEMENTS - Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ACCOUNTING PRONOUNCEMENTS.
Distributed earnings received from equity investments	$ (163)	$ (119)	$ (115)
Adjustment \| Early Adoption \| ASU 2016-15, Statement of Cash Flows
ACCOUNTING PRONOUNCEMENTS.
Cumulative distributions in excess of equity earnings		(25)	(27)
Distributed earnings received from equity investments		$ (25)	$ (27)

EQUITY INVESTMENTS (Details) - USD ($) $ in Millions		1 Months Ended		3 Months Ended								12 Months Ended
EQUITY INVESTMENTS (Details) - USD ($) $ in Millions	Dec. 31, 2015	Aug. 31, 2016	Apr. 30, 2006	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2016
EQUITY INVESTMENTS
Equity Earnings				$ 28	$ 24	$ 22	$ 42	$ 34	$ 17	$ 15	$ 31	$ 116	$ 97	$ 88
Equity Investments	$ 965			1,044				965				1,044	965
Impairment of equity-method investment								199					199
LIABILITIES AND PARTNERS' EQUITY
Current portion of long-term debt	14			23				14				23	14
Amount borrowed												209	618	35
Nonrecurring fair value measurement
EQUITY INVESTMENTS
Impairment of equity-method investment												$ 0	0	0
Northern Border
EQUITY INVESTMENTS
Partnership interest held (as a percent)												50.00%
LIABILITIES AND PARTNERS' EQUITY
Current portion of long-term debt		$ 100
Northern Border \| Revolving credit facility \| Revolving Credit Agreement Expiring 2020
LIABILITIES AND PARTNERS' EQUITY
Amount borrowed		$ 200
Great Lakes
EQUITY INVESTMENTS
Partnership interest held (as a percent)												46.45%
Total cash call issued to fund debt repayment				10			9	10			$ 9
LIABILITIES AND PARTNERS' EQUITY
Current portion of long-term debt	19			$ 19				19				$ 19	19
Northern Border
EQUITY INVESTMENTS
Ownership interest (as a percent)				50.00%								50.00%
Equity Earnings												$ 69	66	69
Equity Investments	480			$ 444				480				$ 444	480
Amortization period of transaction fee			12 years
Transaction fee			$ 10
Additional ownership interest acquired (as a percent)			20.00%
Ownership interest (as a percent)				50.00%								50.00%
Undistributed earnings												$ 0	0	0
Amount of difference between the carrying value and the underlying equity in net assets resulting from the recognition and inclusion of goodwill	116			$ 116				116				116	116
Assets
Cash and cash equivalents	27			14				27				14	27
Other current assets	33			36				33				36	33
Plant, property and equipment, net	1,124			1,089				1,124				1,089	1,124
Other assets	16			14				16				14	16
Assets, total	1,200			1,153				1,200				1,153	1,200
LIABILITIES AND PARTNERS' EQUITY
Current liabilities	39			38				39				38	39
Deferred credits and other	26			28				26				28	26
Long-term debt, net	409			430				409				430	409
Partners' equity
Partners' equity	728			659				728				659	728
Accumulated other comprehensive loss	(2)			(2)				(2)				(2)	(2)
Liabilities and Partners' Equity, total	1,200			$ 1,153				$ 1,200				1,153	1,200
Revenues (expenses)
Transmission revenues												292	286	293
Operating expenses												(72)	(70)	(72)
Depreciation												(59)	(60)	(59)
Financial charges and other												(21)	(22)	(22)
Net income												140	$ 134	140
Northern Border \| Nonrecurring fair value measurement
EQUITY INVESTMENTS
Impairment of equity-method investment	$ 0											$ 0
Northern Border \| ONEOK Partners, L.P.
EQUITY INVESTMENTS
Ownership interest (as a percent)				50.00%								50.00%
Great Lakes
EQUITY INVESTMENTS
Ownership interest (as a percent)	46.45%			46.45%				46.45%			46.45%	46.45%	46.45%
Equity Earnings												$ 28	$ 31	19
Equity Investments	$ 485			$ 474				$ 485				474	485
Undistributed earnings												0	0	0
Equity contribution				5			$ 4	5			$ 4	9	9	9
Assets
Current assets	86			66				86				66	86
Plant, property and equipment, net	727			714				727				714	727
Assets, total	813			780				813				780	813
LIABILITIES AND PARTNERS' EQUITY
Current liabilities	31			40				31				40	31
Long-term debt, net	297			278				297				278	297
Partners' equity
Partners' equity	485			462				485				462	485
Liabilities and Partners' Equity, total	813			$ 780				813				780	813
Revenues (expenses)
Transmission revenues												179	177	146
Operating expenses												(69)	(59)	(53)
Depreciation												(28)	(28)	(28)
Financial charges and other												(21)	(23)	(25)
Net income												$ 61	67	$ 40
Great Lakes \| Nonrecurring fair value measurement
EQUITY INVESTMENTS
Impairment of equity-method investment								199					199
Amount of difference between the carrying value and the underlying equity in net assets resulting from the recognition and inclusion of goodwill	260							260					260
Great Lakes \| TransCanada
EQUITY INVESTMENTS
Ownership interest (as a percent)				53.55%								53.55%
Portland Natural Gas Transmission System
EQUITY INVESTMENTS
Ownership interest (as a percent)				49.90%								49.90%			49.90%
Equity Earnings												$ 19
Equity Investments				$ 126								$ 126
TC PipeLines Intermediate Limited Partnership
EQUITY INVESTMENTS
Partnership interest held (as a percent)												98.9899%
TC GL Intermediate Limited Partnership
EQUITY INVESTMENTS
Partnership interest held (as a percent)												98.9899%
ASU 2015-03, Interest - Imputation of Interest \| Adjustment \| Northern Border
Assets
Other assets	(2)							(2)					(2)
LIABILITIES AND PARTNERS' EQUITY
Long-term debt, net	$ (2)							$ (2)					$ (2)

PLANT, PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
PLANT, PROPERTY AND EQUIPMENT
Cost	$ 2,773	$ 2,760
Accumulated Depreciation	(892)	(811)
Net Book Value	1,881	1,949
Pipeline
PLANT, PROPERTY AND EQUIPMENT
Cost	2,091	2,086
Accumulated Depreciation	(701)	(638)
Net Book Value	1,390	1,448
Compression
PLANT, PROPERTY AND EQUIPMENT
Cost	519	516
Accumulated Depreciation	(148)	(134)
Net Book Value	371	382
Metering and other equipment
PLANT, PROPERTY AND EQUIPMENT
Cost	159	156
Accumulated Depreciation	(43)	(39)
Net Book Value	116	117
Construction in progress
PLANT, PROPERTY AND EQUIPMENT
Cost	4	2
Net Book Value	$ 4	$ 2

ACQUISITIONS - Acquisition of Ownership Interest in PNGTS (Details) - Portland Natural Gas Transmission System - USD ($) $ in Millions	Jan. 01, 2016	Dec. 31, 2016
Acquisition
Interest acquired (as a percent)	49.90%	49.90%
TransCanada \| Transaction between entities under common control
Acquisition
Total purchase price	$ 228
Net purchase price	193
Less: TransCanada's carrying value of non-controlling interest	120
Excess purchase price	73
Purchase price adjustments	5
Assumption of proportional debt	35
Additional contingent payment, minimum	5
Additional contingent payment, maximum	$ 50
Period following closing date during which additional payments may be required	15 years

ACQUISITIONS - 2015 GTN Acquisition Summary and Terms of New Class B Units (Details) - USD ($)			9 Months Ended	12 Months Ended
	Feb. 14, 2017	Apr. 01, 2015	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Acquisition
Equity contribution					$ 2,000,000
TransCanada \| GTN
Noncontrolling interest
Remaining noncontrolling ownership interest (as a percent)						30.00%
General Partner
Acquisition
Equity contribution		$ 2,000,000			2,000,000
GTN
Acquisition
Reduction in Partners' Equity					359,000,000
GTN \| General Partner
Acquisition
Reduction in Partners' Equity					3,000,000
GTN \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control
Acquisition
Interest acquired (as a percent)		30.00%
Purchase price adjustments		$ 11,000,000
Purchase price		457,000,000
Total cash consideration		264,000,000
Assumption of proportional debt		98,000,000
Net purchase price		359,000,000
Less: TransCanada's carrying value of non-controlling interest		232,000,000
Excess purchase price		127,000,000
GTN \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control \| Previously reported
Acquisition
Purchase price		446,000,000
GTN \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control \| General Partner
Acquisition
Reduction in Partners' Equity		$ 127,000,000
Partnership interest \| Class B units \| GTN \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control
Acquisition
Units issued (in units)		1,900,000
Value per unit (in dollars per unit)		$ 50
Equity issuance		$ 95,000,000
GTN \| Class B units \| TransCanada \| Distributions
Distributions
Portion of GTN's annual distributions to which the Class B units are entitled to receive a percentage share of the distributions above threshold (as a percent)		30.00%		30.00%
Percentage applied to 30 percent of GTN's distributions above threshold through March 31, 2020		100.00%
Threshold of 30 percent of GTN's annual distributions for payment to Class B units at specified percentage		$ 20,000,000		$ 20,000,000	15,000,000
Percentage applied to 30 percent of GTN's distributions above threshold after March 31, 2020		25.00%
Percentage applied to GTN's distributable cash flow			30.00%	30.00%
Threshold of GTN's distributions for payment to Class B units	$ 20,000,000		$ 15,000,000	$ 20,000,000	$ 15,000,000

ACQUISITIONS - 2014 Bison Acquisition (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 01, 2014	Dec. 31, 2014	Dec. 31, 2016	Apr. 01, 2015	Sep. 30, 2014
Bison
Acquisitions
Reduction in Partners' Equity		$ 217
Bison \| Limited Partners \| Common units
Acquisitions
Reduction in Partners' Equity		$ 29
Bison \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control
Acquisitions
Interest acquired by Partnership (as a percent)	30.00%		30.00%	30.00%
Purchase price adjustments	$ 2
Total cash consideration	217
TransCanada's carrying value of non-controlling interest	188
Excess purchase price	29
Bison \| Former parent, TransCanada subsidiaries \| Transaction between entities under common control \| Previously reported
Acquisitions
Purchase price	215
Bison \| Former parent, TransCanada subsidiaries \| Limited Partners \| Transaction between entities under common control \| Common units
Acquisitions
Reduction in Partners' Equity	$ 29
Bison \| TransCanada
Acquisitions
Remaining noncontrolling ownership interest (as a percent)					30.00%

DEBT AND CREDIT FACILITIES - Amounts Outstanding and Description of Terms (Details) - USD ($)						12 Months Ended
	Dec. 31, 2016	Sep. 30, 2015	Mar. 13, 2015	Jul. 02, 2013	Jul. 01, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 29, 2016	Jun. 01, 2015
Credit facilities, short-term loan facility and long-term debt
Other assets	$ 1,000,000					$ 1,000,000	$ 1,000,000
Long-term debt	1,867,000,000					1,867,000,000
Less: unamortized debt issuance costs and debt discount	9,000,000					9,000,000	8,000,000
Less: current portion	23,000,000					23,000,000	14,000,000
Total credit facilities, short-term loan facility and long-term debt 10K	1,867,000,000					1,867,000,000	1,911,000,000
Long-term debt	$ 1,835,000,000					1,835,000,000	1,889,000,000
Amount borrowed						$ 209,000,000	618,000,000	$ 35,000,000
Senior Credit Facility and the Term Loan Facilities due in 2018
Credit facilities, short-term loan facility and long-term debt
Leverage ratio, actual (as a percent)	401.00%					401.00%
Senior Credit Facility and the Term Loan Facilities due in 2018 \| Debt agreement covenants, initial period after occurrence of acquisition
Credit facilities, short-term loan facility and long-term debt
Additional period immediately following the fiscal quarter in which a specified material acquisition occurs						6 months
Senior Credit Facility and the Term Loan Facilities due in 2018 \| Debt agreement covenants, initial period after occurrence of acquisition \| Maximum
Credit facilities, short-term loan facility and long-term debt
Leverage ratio, covenant (as a percent)						550.00%
Senior Credit Facility and the Term Loan Facilities due in 2018 \| Debt agreement covenants, periods subsequent to initial period after occurrence of acquisition \| Maximum
Credit facilities, short-term loan facility and long-term debt
Leverage ratio, covenant (as a percent)						500.00%
Revolving credit facility \| TC Pipelines, LP Senior Credit Facility due 2021
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	$ 160,000,000					$ 160,000,000	$ 200,000,000
Weighted Average Interest Rate (as a percent)						1.72%	1.44%
Maximum borrowing capacity	500,000,000					$ 500,000,000
Amount outstanding under credit facility	160,000,000					160,000,000	$ 200,000,000
Remaining borrowing capacity	340,000,000					340,000,000
Revolving credit facility \| TC Pipelines, LP Senior Credit Facility due 2021 \| Maximum
Credit facilities, short-term loan facility and long-term debt
Increase in credit facility	$ 500,000,000					$ 500,000,000
Revolving credit facility \| TC Pipelines, LP Senior Credit Facility due 2021 \| LIBOR
Credit facilities, short-term loan facility and long-term debt
Debt interest rate, at period end (as a percent)	1.92%					1.92%	1.50%
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	$ 500,000,000					$ 500,000,000	$ 500,000,000
Weighted Average Interest Rate (as a percent)						1.73%	1.44%
Amount of debt					$ 500,000,000
Borrowings under the facility				$ 500,000,000
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018 \| Base rate borrowings \| Federal funds rate
Credit facilities, short-term loan facility and long-term debt
Basis spread on variable rate (as a percent)					0.50%
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018 \| Base rate borrowings \| LIBOR
Credit facilities, short-term loan facility and long-term debt
Basis spread on variable rate (as a percent)					1.00%
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018 \| Base rate borrowings \| Base rate \| Minimum
Credit facilities, short-term loan facility and long-term debt
Basis spread on variable rate (as a percent)					0.125%
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018 \| Base rate borrowings \| Base rate \| Maximum
Credit facilities, short-term loan facility and long-term debt
Basis spread on variable rate (as a percent)					1.00%
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018 \| LIBOR borrowings \| LIBOR
Credit facilities, short-term loan facility and long-term debt
Weighted Average Interest Rate (as a percent)						2.31%	2.79%
Debt interest rate, at period end (as a percent)	1.87%					1.87%	1.50%
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018 \| LIBOR borrowings \| LIBOR \| Minimum
Credit facilities, short-term loan facility and long-term debt
Basis spread on variable rate (as a percent)					1.125%
Term loan \| TC PipeLines, LP 2013 Term Loan Facility due 2018 \| LIBOR borrowings \| LIBOR \| Maximum
Credit facilities, short-term loan facility and long-term debt
Basis spread on variable rate (as a percent)					2.00%
Term loan \| TC PipeLines, LP 2015 Term Loan Facility due 2018
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	$ 170,000,000					$ 170,000,000	$ 170,000,000
Weighted Average Interest Rate (as a percent)						1.63%	1.47%
Amount of debt		$ 170,000,000
Amount borrowed		$ 170,000,000
Term loan \| TC PipeLines, LP 2015 Term Loan Facility due 2018 \| LIBOR
Credit facilities, short-term loan facility and long-term debt
Debt interest rate, at period end (as a percent)	1.77%					1.77%	1.39%
Unsecured debt \| TC PipeLines, LP 4.65% Senior Notes due 2021
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	4.65%					4.65%	4.65%
Debt and credit facilities	$ 350,000,000					$ 350,000,000	$ 350,000,000
Weighted Average Interest Rate (as a percent)						4.65%	4.65%
Unsecured debt \| TC PipeLines, LP 4.375% Senior Notes due 2025
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	4.375%		4.375%			4.375%	4.375%
Debt and credit facilities	$ 350,000,000					$ 350,000,000	$ 350,000,000
Weighted Average Interest Rate (as a percent)						4.375%	4.375%
Amount of debt			$ 350,000,000
Net proceeds			$ 346,000,000
Unsecured debt \| GTN 5.29% Senior Notes due 2020
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	5.29%					5.29%	5.29%
Unsecured debt \| GTN 5.69% Senior Notes due 2035
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	5.69%					5.69%	5.69%
Secured debt \| Tuscarora 3.82% Series D Senior Notes due 2017
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	3.82%					3.82%	3.82%
GTN
Credit facilities, short-term loan facility and long-term debt
Percentage of debt to total capitalization, actual	44.50%					44.50%
GTN \| 5.09% Senior Notes due 2015
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)										5.09%
GTN \| Unsecured debt \| GTN 5.29% Senior Notes due 2020
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	$ 100,000,000					$ 100,000,000	$ 100,000,000
Weighted Average Interest Rate (as a percent)						5.29%	5.29%
GTN \| Unsecured debt \| GTN 5.69% Senior Notes due 2035
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	150,000,000					$ 150,000,000	$ 150,000,000
Weighted Average Interest Rate (as a percent)						5.69%	5.69%
GTN \| Unsecured debt \| GTN Term Loan Facility due 2019
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	$ 65,000,000					$ 65,000,000	$ 75,000,000
Weighted Average Interest Rate (as a percent)						1.43%	1.15%
GTN \| Unsecured debt \| GTN Term Loan Facility due 2019 \| LIBOR
Credit facilities, short-term loan facility and long-term debt
Debt interest rate, at period end (as a percent)	1.57%					1.57%	1.19%
Amount of debt										$ 75,000,000
GTN \| Unsecured debt \| Senior Notes and Term Loan Facility due 2019 \| Maximum
Credit facilities, short-term loan facility and long-term debt
Percentage of debt to total capitalization, covenant						70.00%
Tuscarora Gas Transmission Company
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	$ 10,000,000					$ 10,000,000
Weighted Average Interest Rate (as a percent)						1.64%
Tuscarora Gas Transmission Company \| Unsecured debt \| Tuscarora Term Loan due 2019
Credit facilities, short-term loan facility and long-term debt
Amount of debt									$ 9,500,000
Tuscarora Gas Transmission Company \| Unsecured debt \| Tuscarora Term Loan due 2019 \| LIBOR
Credit facilities, short-term loan facility and long-term debt
Debt interest rate, at period end (as a percent)	1.90%					1.90%
Tuscarora Gas Transmission Company \| Unsecured debt \| Tuscarora 3.82% Series D Senior Notes due 2017
Credit facilities, short-term loan facility and long-term debt
Percentage of debt to total capitalization, actual	21.22%					21.22%
Debt Service Coverage, Actual (as a percent)	415.00%
Tuscarora Gas Transmission Company \| Unsecured debt \| Tuscarora 3.82% Series D Senior Notes due 2017 \| Minimum
Credit facilities, short-term loan facility and long-term debt
Debt Service Coverage, covenant (as a percent)	300.00%
Tuscarora Gas Transmission Company \| Unsecured debt \| Tuscarora 3.82% Series D Senior Notes due 2017 \| Maximum
Credit facilities, short-term loan facility and long-term debt
Percentage of debt to total capitalization, covenant	45.00%
Tuscarora Gas Transmission Company \| Secured debt \| Tuscarora 3.82% Series D Senior Notes due 2017
Credit facilities, short-term loan facility and long-term debt
Debt and credit facilities	$ 12,000,000					$ 12,000,000	$ 16,000,000
Weighted Average Interest Rate (as a percent)						3.82%	3.82%
ASU 2015-03, Interest - Imputation of Interest \| Adjustment
Credit facilities, short-term loan facility and long-term debt
Other assets							$ (7,000,000)
Long-term debt							(7,000,000)
Long-term debt							$ (7,000,000)

DEBT AND CREDIT FACILITIES - Principal Payments Required (Details) $ in Millions	Dec. 31, 2016 USD ($)
Principal repayments required on debt
2017	$ 23
2018	691
2019	43
2020	100
2021	510
Thereafter	500
Total debt	$ 1,867

OTHER LIABILITIES (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
OTHER LIABILITIES
Regulatory liabilities	$ 25	$ 24
Other liabilities	3	3
Other liabilities, total	$ 28	$ 27

PARTNERS' EQUITY - Ownership (Details) - shares		12 Months Ended
PARTNERS' EQUITY - Ownership (Details) - shares	Apr. 01, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common units
Partners' Equity
Common units outstanding, end of year (in units)		67,400,000	64,300,000	63,600,000
Common units \| Limited Partners
Partners' Equity
Common units outstanding, end of year (in units)		67,454,831
Non-affiliates \| Common units \| Limited Partners
Partners' Equity
Common units outstanding, end of year (in units)		50,370,000
TC PipeLines GP, Inc. \| General Partner
Partners' Equity
IDRs ownership (as a percent)		100.00%
Ownership interest in the Partnership (as a percent)	2.00%	2.00%	2.00%	2.00%
TC PipeLines GP, Inc. \| Common units \| Limited Partners
Partners' Equity
Common units outstanding, end of year (in units)		5,797,106
TransCanada Corporation and subsidiaries \| Common units \| Limited Partners
Partners' Equity
Common units outstanding, end of year (in units)		17,084,831
TransCanada \| Common units \| Limited Partners
Partners' Equity
Common units outstanding, end of year (in units)		11,287,725
Ownership interest in the Partnership (as a percent)		25.30%
TransCanada \| Class B units \| Limited Partners
Partners' Equity
Common units outstanding, end of year (in units)		1,900,000
Ownership interest in the Partnership (as a percent)		100.00%

PARTNERS' EQUITY - ATM Equity Issuance Program (Details)

2 Months Ended

3 Months Ended

12 Months Ended

Aug. 05, 2016

USD ($)

item

Apr. 01, 2015

USD ($)

May 19, 2016

USD ($)

item

$ / shares

May 19, 2016

Dec. 31, 2016

USD ($)

Dec. 31, 2015

USD ($)

Dec. 31, 2014

USD ($)

Aug. 31, 2014

USD ($)

Net proceeds from public offering of common units

^[1]

$ 83,000,000

Equity contribution

$ 2,000,000

Common units issuance subject to rescission net

83,000,000

Common units subject to rescission

83,000,000

General Partner

Net proceeds from public offering of common units

^[1]

$ 2,000,000

Equity contribution

$ 2,000,000

TC PipeLines GP, Inc. | General Partner

Ownership interest in the Partnership (as a percent)

2.00%

ATM Equity Issuance Program | Common units

Aggregate offering price of units

$ 200,000,000

Units sold | shares

1,619,631

3,100,000

700,000

1,300,000

Net proceeds from issuance of common units

$ 164,000,000

$ 43,000,000

$ 71,000,000

Sales agent commissions

2,000,000

400,000

1,000,000

Common units issuance subject to rescission net

$ 82,334,015

Number of unitholders that have claimed or exercised any rescission rights to date | item

ATM Equity Issuance Program | TC PipeLines GP, Inc. | General Partner

ATM Equity Issuance Program | Minimum | Common units

Equity contribution

$ 3,000,000

$ 1,000,000

$ 2,000,000

Common units (price per unit) | $ / shares

$ 47.00

ATM Equity Issuance Program | Maximum | Common units

Common units (price per unit) | $ / shares

$ 54.95

Period of time for Section 5 Securities violations to be filed within

1 year

Equity Distribution Agreement (EDA) | Common units