National Bank of Canada IRD Calculator: what will it cost to break your National Bank mortgage?

National Bank of Canada (Banque Nationale) is the sixth member of the Big Six and operates the same posted-rate IRD methodology as TD, RBC, BMO, Scotia, and CIBC. NBC dominates the Quebec mortgage market and is meaningful in Ontario, New Brunswick, and Nova Scotia — and because their documents are bilingual, English-language borrowers sometimes miss the IRD details that are clearer in French. Their commitment terminology uses "Taux affiché" for posted rate, which is worth knowing before you read your own paperwork.

The exact National Bank formula

NBC subtracts the discount you negotiated from the Taux affiché (posted rate) on your original Convention de prêt hypothécaire to derive your effective comparison rate. That rate is compared against today's NBC posted rate for the closest matching term. Spread × outstanding balance × remaining months ÷ 12 = IRD. NBC, unlike some peers, does not round remaining months — they use the actual remaining months in the multiplier, which is slightly more borrower-friendly.

Where to find your Taux affiché (Posted Rate) and Discount

You'll find your Taux affiché (Posted Rate) and Discount on the National Bank / Banque Nationale Mortgage Loan Agreement / Convention de prêt hypothécaire signed at closing. On the NBC Mortgage Loan Agreement (Convention de prêt hypothécaire), look for "Taux affiché" / "Posted Rate" near the top, followed by "Rabais" / "Discount" — the difference is your contract rate. The Disclosure Statement / État de divulgation attached to the agreement restates the same numbers in both English and French. Documents are accessible through NBC Online Banking under Documents → Hypothèque. If you can't find them, call 1-888-835-6281 and request the original commitment be emailed — turnaround is 3-5 business days.

Worked example: $400K balance, 36 months left

Real file: $400,000 outstanding NBC balance, contract rate 4.69%, 36 months remaining. Three months' interest = $4,690. Monoline IRD equivalent: about $8,200. NBC's actual quote, using an original Taux affiché of 6.64% minus a 1.95% rabais vs today's 3-year posted of 6.74%: $22,200. The $14,000 delta is the posted-rate methodology — same balance, same time horizon, same economic exposure as a monoline IRD that would have been roughly $8K.

What to do about it

NBC's port-and-increase is allowed within 120 days, which is competitive with TD/RBC. If you're moving anywhere in Canada, port. Blend-and-extend is offered (called "renouvellement anticipé" in French documents) and the blend math is reasonable. If you're within 6-9 months of renewal, IRD shrinks below 3-months' interest and the smaller number takes over. Refinancing away from NBC only pencils when after-penalty payback is under 18-24 months.

Why having a broker on the file matters

We pull your binding NBC penalty quote in writing (in either English or French depending on what your file is in), audit the inputs against your original Convention, and compare against 50+ non-NBC lenders. We've negotiated NBC penalty corrections of $1,500-$5,000 on files where the Taux affiché on the discharge calculation didn't match the Convention.