"No interest if paid in full" is not the same as 0% APR.

Two promotions that sound alike

The CFPB describes a card that promises no interest on a purchase if paid in full within a period as a deferred-interest plan. If the balance is not fully paid by the end of the period, interest is charged from the purchase date, typically on the balance you owed in each month since the purchase. [1] A 0% intro APR works differently: no interest accrues during the promotion, and any remaining balance starts accruing at the regular APR only after it ends.

Worked example: $60 left over

The purchase and APR are invented. A $1,200 purchase has a 12-month promotion and a 26.99% standard APR. The buyer pays $95 a month. After 12 payments, $60 remains.

Under a deferred-interest plan, this simple model charges interest on each month's starting balance at 26.99% / 12, from $1,200 down to $155. That totals about $182.86, all added at once when the promotion ends, on top of the $60 still owed. Under a true 0% intro APR, the same buyer owes the $60 with no back interest, and interest starts only on that $60 going forward.

Paying $100 a month instead clears the balance in 12 payments, so neither promotion charges interest. The difference between the two outcomes is $5 a month. Real issuers use daily balances and their own billing cycles, so treat these figures as a model of the mechanism, not a quote.

A payoff routine for a promotion you already have

• Find the promotion end date on the statement; the CFPB notes it may differ from your regular due date. [1]
• Divide the promotional balance by the number of payments left before that date, then round up, and set that amount as a fixed autopay.
• Avoid new purchases on the same card if you do not pay the full statement balance; the CFPB warns other purchases may lose the grace period. [1]
• If the card carries other balances, remember that extra payments go to higher-APR balances until the final two billing cycles. [1][2]
• Aim to finish one billing cycle early to absorb a processing delay.

Traps that turn a small balance into a large charge

• Paying only the minimum: the CFPB says minimums often will not clear the purchase before the deadline. [1]
• Mixing new purchases on the same card: extra payments can go to other higher-APR balances first until the last two billing cycles. [1][2]
• Assuming the due date is the deadline: the promotion end date can differ from the regular payment due date. [1]
• Missing a payment by more than 60 days: the CFPB says this can end the promotion early. [1]
• Leaving a few dollars unpaid: under deferred interest, any remaining balance can trigger interest on the balances you carried in each month since the purchase. [1]

Before you accept a new promotion

Ask whether the offer is deferred interest or a 0% intro APR, and only accept a deferred-interest plan if the full monthly payoff amount fits your budget with a margin. If you can pay the purchase in full now or from savings without disturbing your emergency cushion, skipping the promotion avoids the deadline risk entirely. In a 2017 announcement, the CFPB encouraged retail card issuers to consider more transparent zero-percent promotions instead of deferred interest. [3] This guide is US consumer education, not personalized advice.