BMO Bank of Montreal IRD Calculator: what will it cost to break your BMO mortgage?

BMO's IRD formula is the cleanest-documented of the Big Six — their commitment letter spells out the methodology in plain language — but cleanly documented doesn't mean cheap. BMO uses posted-rate IRD just like every other Big Six bank, and on a typical 5-year fixed with 30+ months remaining, their penalty quotes routinely come in at 4-6x what a monoline would charge on identical economics.

The exact BMO formula

BMO compares your "Annual Interest Rate" (the discounted contract rate that appears at the top of your commitment) against today's BMO posted rate for the term closest in length to your remaining months — but the trick is, they reconstruct your effective rate using the original posted rate at signing minus your "Discount from Posted." If the original posted-vs-current-posted spread is wider than the contract-vs-current-contract spread, BMO uses the wider number. Spread × balance × remaining months ÷ 12 = IRD.

Where to find your Annual Interest Rate and Discount from Posted

You'll find your Annual Interest Rate and Discount from Posted on the BMO Mortgage Commitment letter and the BMO Disclosure Statement signed at closing. Two BMO documents matter. First, the BMO Mortgage Commitment letter you signed before funding — look near the top for "Annual Interest Rate" (your contract rate) and "Discount from Posted" (the rate reduction). Second, the Disclosure Statement attached at closing restates both numbers. Both are in BMO Online Banking under My Documents → Mortgage if signed digitally. If you can't find either, call 1-866-262-1618 and ask for the original commitment letter to be emailed — it takes 2-4 business days.

Worked example: $400K balance, 36 months left

Real file: $400,000 outstanding BMO balance, contract rate 4.74%, 36 months remaining. Three months' interest = $4,740. Monoline equivalent IRD: roughly $8,300. BMO's quote, with an original posted of 6.69% minus a 1.95% Discount from Posted vs today's 3-year posted of 6.79%: $22,700. The $14,400 gap is the posted-rate methodology — pure overhead that has no underlying economic basis but is contractually permitted under your commitment.

What to do about it

BMO's port-and-increase program is reasonably flexible (120 days, most provinces). If you're moving, port. If you're refinancing, ask BMO for a blend-and-extend; their blend rates are competitive when they want to keep you. If breaking is the only option, use the Sanity Check above to confirm payback is under 18-24 months. Within 9 months of renewal, IRD shrinks below 3-months' interest and 3-months' interest takes over — sometimes worth waiting.

Why having a broker on the file matters

We pull your real BMO penalty quote in writing, audit it against your commitment letter's documented methodology, and present a clean side-by-side: stay-at-BMO blend, refinance to a non-BMO lender, or wait for renewal. We've negotiated BMO penalty reductions of $2,500-$6,000 on files where BMO's first quote used the wrong remaining-term bucket.