Hustle & GritWatch us on YouTube
The interest rate differential (IRD) is a prepayment penalty formula that charges the difference between a mortgage’s contract rate and the lender’s current comparison rate, applied to the outstanding balance for the time remaining in the term. It typically applies to fixed-rate mortgages broken before maturity, and is charged only if it is larger than three months’ interest.
The interest rate differential (IRD) compares the rate a borrower locked in against the rate the lender could get today for the time remaining on the term, and charges the difference on the outstanding balance. It exists because breaking a fixed-rate contract early costs the lender the interest it was expecting to earn.
The tricky part is the comparison rate: each lender defines its own, typically its posted rate for a term matching however much time is left. That’s why two lenders can quote very different IRD amounts on what looks like the same mortgage.
IRD is only charged if it’s larger than three months’ interest — the two aren’t added together. When rates have risen since the mortgage was signed, IRD often shrinks toward zero and three months’ interest becomes the operative prepayment penalty instead.
IRD = Balance × (Contract rate − Comparison rate) × (Months remaining ÷ 12)
Comparison rate varies by lender: each lender picks its own comparison rate, often its posted rate for a term matching the time left on the mortgage, which is why IRD quotes differ between lenders on the same file.
Only the larger of two charges applies: a fixed-rate mortgage is typically penalized using whichever is bigger, the IRD or three months’ interest — never both.
Rate environment matters: IRD tends to be larger when the contract rate is well above the comparison rate, and can shrink toward zero when rates have moved the other way.
Who requests the quote: mortgage agents (Ontario, FSRA), submortgage brokers (BC, BCFSA), mortgage associates (Alberta, RECA), and courtiers hypothécaires (Quebec, AMF) ask the lender for a written IRD quote before a client commits to breaking a term.
A borrower has 24 months left on a 5-year fixed mortgage with a $400,000 balance at a contract rate of 5.49%. The lender’s current comparison rate for a 2-year term is 3.99% (fictional rates, for illustration only):
$400,000 × 1.50% × 2.0 = $12,000. This example’s three months’ interest would be $5,490 (see the Three Months’ Interest Penalty example) — since IRD is larger, IRD is the charge.
Definitions reflect Canadian federal and provincial rules as of the “Updated” date above. Not advice for any specific file.
Every term a Canadian mortgage professional needs — defined, sourced, and kept current.
See how Treadstone can scale your brokerage — a free call, no commitment.