I transferred a balance at a zero percent rate and have been paying the minimum amount due each month. I made a purchase and was charged interest on the purchase. How can that be?
Card issuers have different rules about when they charge interest. For most issuers, if you carry a balance month to month, any purchases you make will accrue interest from the date of the transaction. This is true even if the balance you are carrying is not subject to interest because it was a 0% balance transfer.
Your cardholder agreement should tell you the rules your card issuer applies. You should be able to find a copy of the agreement on your card issuer’s website, and you can request a copy of the agreement from your card issuer if it is not there.