Three months' interest versus the IRD
Break a fixed-rate mortgage early and you pay the greater of two amounts. Three months' interest is simple: your balance times your monthly rate, times three. The Interest Rate Differential recovers the interest the lender expected to earn over the rest of your term, and on a long remaining term at a high rate it is usually the bigger of the two. Variable-rate mortgages are simpler — the penalty is just three months' interest.
Why the bank's number is often higher
The standard IRD compares your rate to the lender's current rate for a comparable term. The Big Five banks instead compare your rate to their posted rate minus the discount you originally received, which inflates the gap and the penalty. This tool uses the standard method, so treat its IRD as a floor and confirm the exact figure with your lender before you act.
Before you break your mortgage
Sometimes the penalty is worth paying — to refinance at a much lower rate, consolidate debt, or sell. Run the numbers, then keep the paperwork. A durable record of your mortgage history, rates, and renewal dates is the cheapest insurance a homeowner has, and it is what Habyn property records are built to keep, free for homeowners on the Home plan.