Any promotional interest-free period on purchases will begin on the day your card is approved, which may be several days earlier than the day on which you actually receive your card and are able to begin using it. So it’s important to make a note of the date on which your card application was approved. Then put a reminder in your paper or electronic diary, three, six, nine or twelve months ahead (depending on the length of your interest-free period), to alert you to the fact that your interest-free period is about to expire. In fact, make that diary note, and plan to pay off your purchase balance, a couple of days ahead of the expiry date, to allow for payment processing delays or the occurrence of non-banking days such as weekends. Suppose you had accumulated a purchase balance of $25,000 over 12 months. If you were three days late making the payment to clear the balance, at a revert rate of 20% you’d end up paying $41 in unnecessary interest, and you’d probably incur a late payment fee as well.