How a credit card actually charges you
A credit card doesn’t charge you day by day. It charges you in cycles, and inside every cycle there’s a window where borrowing costs nothing at all. Most of the confusion about credit card interest comes down to where that window starts and where it closes.
The cycle, not the calendar month
Your card has a billing cycle. It’s usually about a month long, but it almost never lines up with the first and last day of the month. Somewhere in there is a closing date. Everything you bought since the last closing date gets totalled up, and that total becomes your statement balance.
After the cycle closes, you get a statement and a due date. In Canada, if your card is from a bank or another federally regulated institution, the law sets a floor on how far away that due date can be.
A bank cannot set your credit card payment due date sooner than 21 days after the billing cycle closes.
Scope. Applies to banks and other federally regulated financial institutions. Provincially regulated credit unions and some retail cards fall under provincial rules instead. The section sets a minimum, so an individual card may allow more time.
So there are two dates that matter, and they’re different: the day the cycle closes, and the day the payment is due. The gap between them is your breathing room.
Two balances, two meanings
Open your banking app and you’ll usually see two numbers, and they rarely match.
Your current balance is what you owe right now, this second, including things you bought after the cycle closed. Your statement balance is the frozen total from the last cycle, and it’s the number the due date refers to.
Paying the statement balance in full by the due date is the thing that matters. Your current balance can be higher than that and you’re still fine, because the newer purchases belong to the next cycle. This trips up a lot of people, and there’s nothing obvious about it.
The grace period is real, and it’s free
Here’s the part that makes credit cards usable. If you pay the whole statement balance by the due date, the purchases in that cycle cost you nothing in interest. Not a reduced amount. Zero.
No interest is charged on purchases made during a billing cycle if you pay the outstanding balance in full by the due date.
Scope. Applies to purchases at banks and other federally regulated institutions. The protection is conditional: it attaches only when the outstanding balance is paid in full by the due date, and the statute says nothing about what you are charged when it is not. It does not extend to cash advances, cash-like transactions, or balance transfers, and it does not apply to a balance carried over from an earlier cycle. Provincially regulated credit unions sit outside the Bank Act.
That’s the whole mechanism behind cashback being worth anything. You borrowed the money for a few weeks, gave it back on time, and the borrowing was free.
One exception worth knowing before it surprises you. Cash advances and cash-like transactions don’t get this treatment. They generally start costing you from the day you take them out.
The interest-free grace period does not apply to cash advances, cash-like transactions, or balance transfers. Cash advances and cash-like transactions are charged interest from the day you make them.
Scope. General description of federally regulated credit cards. Which transactions an issuer treats as cash-like is defined in the individual cardholder agreement. For a balance transfer the agency says only that interest is charged, not from when, and a promotional rate can lower it for a set period.
What changes if you don’t pay in full
This is the part almost nobody gets told, and it’s the single most useful thing on this page.
If you don’t clear the statement balance, you lose the grace period. Read the rule above again and notice the condition attached to it: the interest-free window is guaranteed only when you pay the outstanding balance in full by the due date. Miss that, and the guarantee stops applying, to the leftover amount and to the purchases you make after it.
When interest actually starts running is set by your own cardholder agreement, not by one national rule. Issuers are required to tell you the date on and after which interest accrues, and on many cards that date is the day of the purchase. Read that line in your agreement, because it decides whether a charge you made three weeks ago has been quietly accruing interest for three weeks.
Each issuer must disclose the date on and after which interest accrues on your account, and that date is set by your cardholder agreement rather than by a single national rule.
Scope. The law requires the date to be disclosed. It does not fix what that date is. Charging interest back to the purchase date once a balance is revolved is a common issuer practice, but it is not universal and it is not itself the law. The only reliable answer for your own card is the one in your own cardholder agreement.
So the cost of leaving a small amount unpaid is bigger than it looks. The card has started behaving differently, and that change costs more than the leftover balance does.
Getting the grace period back
The good news is that this isn’t permanent, and it isn’t a punishment you have to serve out. Pay a statement’s full balance by its due date and the new purchases on that statement are interest-free again, even if you carried a balance the month before.
Paying a statement’s full balance by its due date makes the new purchases on it interest-free, even if you carried a balance the month before.
Scope. Federally regulated issuers only. This is the agency’s notice from when the rule was introduced, in force from September 2010, and the Bank Act rule cited earlier on this page carries the same condition today. It covers new purchases only and says nothing about interest on the balance carried from the month before. Cash advances fall outside it.
If you’re carrying something you can’t clear in one go, that’s a different situation and it’s covered in what to do when it goes wrong. No judgment attached. It’s common.
The minimum payment
The minimum payment is the smallest amount that keeps your account in good standing. It is not a suggestion about what you should pay, and it isn’t priced to get you out of debt quickly.
Your statement has to tell you roughly how long clearing the balance would take if the minimum were all you ever paid. That disclosure exists because the answer is usually startling.
By law your credit card statement must estimate how long it would take to pay off the balance if you only ever made the minimum payment.
Scope. Applies to banks and other federally regulated institutions. The estimate rests on prescribed assumptions, including that only the minimum payment is made each period and no further purchases occur, so it is an illustration rather than a forecast. It is not required where the balance must be paid in full on receipt of the statement.
Quebec is the exception in Canada. It sets a floor on how low the minimum payment can be, and that floor is higher than what most cards elsewhere ask for.
In Quebec, the monthly minimum payment on a credit card must be at least five percent of the balance on the statement.
Scope. Quebec only, under the provincial Consumer Protection Act, and the level the provincial agency gives as in force today. An issuer may ask for more only if the contract already provided for it. The page does not describe how the floor was phased in or what other provinces require.
Quebec’s floor under the minimum payment took effect in 2019, and no other province had a minimum payment rule from 2018 to 2024.
Scope. A staff working paper, so the views are its authors’ and may differ from the Bank of Canada’s. The rule set five percent for cards opened from August 2019 and two percent for older cards, then raised older cards by half a percentage point each August until they reached five percent in 2025. The paper says that minimums elsewhere in Canada were below those in the US and the UK, and that the rule set Quebec’s well above both. Its check on other provinces covers 2018 to 2024 only.
There’s also a quieter effect worth naming. Simply putting a minimum payment number on a statement seems to pull people’s payments down toward it, even when they could pay more.
Showing a minimum payment amount on a statement pulls down how much people choose to repay.
Scope. A survey of UK cardholders found that partial repayments on their own statements tracked the minimum asked for. An experiment then used mock statements rather than real payments, with campus visitors, web visitors and people recruited by a market research firm, and found the minimum changed how much partial payers repaid, not whether people paid in full. Later lab and field studies find the same direction, and a higher anchor can raise payments. Anchoring is one influence among several: many people pay the minimum because it is what they can afford, which this study does not measure.
That research doesn’t say people are foolish. Plenty of people pay the minimum because the minimum is what they have. It says the number on the page is doing some of the deciding, and it’s worth deciding for yourself instead.
The short version
Pay the statement balance, in full, by the due date. Everything else about credit card interest is detail.