Filed Pursuant to Rule 433

Registration No. 333-221898

October 10, 2018

U.S.$400,000,000
TransCanada PipeLines Limited

Re-Opening of 4.250% Senior Notes due 2028

This Pricing Term Sheet should be read together with the preliminary prospectus supplement of TransCanada PipeLines Limited dated October 10, 2018 (the “Preliminary Prospectus Supplement”). The information in this Pricing Term Sheet supplements the Preliminary Prospectus Supplement and supersedes the information in the Preliminary Prospectus Supplement to the extent inconsistent with the information in the Preliminary Prospectus Supplement. Other information presented in the Preliminary Prospectus Supplement is deemed to have changed to the extent affected by the changes described herein.

In addition to the pricing information set forth above, the Preliminary Prospectus Supplement will be updated to reflect the following changes:

The “Certain Income Tax Considerations—Certain U.S. Federal Income Tax Considerations” section will be amended to add the following paragraph as the seventh paragraph:

Qualified Reopening and Pre-Issuance Accrued Interest

It is anticipated and the following discussion assumes that the issuance of new 2028 Notes offered hereby will constitute a “qualified reopening” of the issuance of the existing 2028 Notes, within the meaning of the applicable U.S. Treasury Regulations. Consequently, for U.S. federal income tax purposes the “issue price” of a new 2028 Note offered hereby will equal the issue price of the existing 2028 Notes (i.e., 99.611% of the principal amount thereof), and the issue date of the new 2028 Notes offered hereby will be considered to be the issue date of the existing 2028 Notes. Additionally, a portion of the price paid for new 2028 Notes offered hereby will be allocable to interest that “accrued” prior to the

issuance of the new 2028 Notes offered hereby, or “pre-issuance accrued interest.” To the extent a portion of a beneficial holder’s purchase price is allocable to pre-issuance accrued interest, a portion of the first stated interest payment equal to the amount of pre-issuance accrued interest will be treated as a nontaxable return of such purchase price to the holder, rather than as interest income. Amounts treated as a return of purchase price will reduce a beneficial holder’s adjusted tax basis in the new 2028 Notes offered hereby by a corresponding amount.

The “Certain Income Tax Considerations—Certain U.S. Federal Income Tax Considerations—Payments of Interest” and “—Sale, Retirement or Other Taxable Disposition of the Notes” sections will be amended to delete in its entirety the text thereof and replace it with the following text:

Payments of Interest

Except as described above with respect to pre-issuance accrued interest paid on the 2028 Notes, each payment of interest on a note will be taxable to a U.S. Holder as ordinary interest income at the time it is accrued or is received in accordance with the U.S. Holder’s method of accounting for U.S. federal income tax purposes. Interest on the notes will constitute income from sources without the U.S. and will be “passive category income” for purposes of computing the foreign tax credit allowable under the U.S. federal income tax laws. The rules governing the foreign tax credit are complex, and U.S. Holders should consult their tax advisors regarding the availability of the credit under their particular circumstances.

Sale, Retirement or Other Taxable Disposition of the Notes

A U.S. Holder will recognize a gain or loss on the sale, retirement or other taxable disposition of a note equal to the difference between the amount realized on the sale or retirement (except to the extent of accrued and unpaid interest, or pre-issuance interest for the 2028 Notes, which will be taxable as ordinary interest income) and the U.S. Holder’s tax basis in the note (generally, the price the U.S. Holder paid for the note decreased, for the 2028 Notes, by any amount attributable to pre-issuance accrued interest that has already been paid to such U.S. Holder and any amortizable bond premium previously amortized). As a general rule, such gain or loss recognized on the sale or retirement of a note will be capital gain or loss and will be long-term capital gain or loss if the note was held for more than one year. Such income or loss will generally constitute income or loss from sources within the U.S. for purposes of computing the foreign tax credit allowable under the U.S. federal income tax laws.

For non-corporate U.S. Holders, including individuals, long-term capital gains generally are taxed at a lower rate than ordinary income. The deductibility of capital losses is subject to limitations.

*Note: A security rating is not a recommendation to buy, sell or hold securities and may be subject to revision or withdrawal at any time.

The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates.  Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering.

You may get these documents for free by visiting EDGAR on the SEC Web site at www.sec.gov.  Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling J.P. Morgan Securities LLC collect at (212) 834-4533 or Deutsche Bank Securities Inc. toll free at (800) 503-4611.

U.S.$1,000,000,000
TransCanada PipeLines Limited

5.100% Senior Notes due 2049

*Note: A security rating is not a recommendation to buy, sell or hold securities and may be subject to revision or withdrawal at any time.

The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates.  Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering.

You may get these documents for free by visiting EDGAR on the SEC Web site at www.sec.gov.  Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling J.P. Morgan Securities LLC collect at (212) 834-4533 or Deutsche Bank Securities Inc. toll free at (800) 503-4611.