Interest Rate Cap

An interest rate cap is a contractual feature that limits how high a variable interest rate can rise, either for a set period or for the life of the mortgage. On a floating-rate mortgage, the lender normally moves your rate up and down with prime, but a cap sets a ceiling the rate cannot exceed.

How a cap works in Canada

Most Canadian variable-rate mortgages have no cap. Your rate floats with the lender's prime rate, which itself responds to the policy interest rate set by the Bank of Canada. When prime rises, an adjustable-rate variable mortgage sees the payment rise, while a static-rate variable mortgage keeps the payment the same and pushes more of it toward interest until the payment may no longer cover the interest owing.

A cap is negotiated with the lender, and sometimes arranged separately as a hedging contract. It is typically written as a maximum rate — for example, prime plus a set margin, capped at a stated ceiling. Because a cap transfers interest-rate risk from the borrower to the lender or counterparty, it usually carries a cost: a higher rate, a fee, or a narrower set of features. Capped variable products appear far more often in commercial and construction lending than in everyday residential mortgages, though some residential lenders have offered them.

Why a cap matters to a borrower

Budgeting is the practical benefit. Borrowers who can absorb rate movement get flexibility, while those who need certainty typically choose a fixed-rate mortgage. A cap sits between the two.

Suppose the cap sits a fixed number of percentage points above your starting rate. If prime climbs past that ceiling, your rate stops there and the lender absorbs the rest. That protects against payment shock and reduces the chance of drifting into negative amortization, where unpaid interest is added back to the balance. The trade-off is the price of the protection and the loss of the full benefit when rates fall.

What to check before you sign

• Does the cap apply to the interest rate, the payment, or both?
• How long does the cap last — the whole term, or only a set window?
• What does it cost, and does it change your rate or other features?
• What happens at renewal when the cap expires?

Read the mortgage commitment closely, since a cap can be drafted to cover only part of the term. Compare the total cost against a fixed rate and a plain variable rate. For background on how these products differ, see the fixed vs variable guide, and confirm the specific terms with the lender.