I paid off my entire bill when it was due last month and still got charged interest. How can that be?
If you've been carrying a balance, most card issuers will charge you interest from the time your bill was sent to you until the time your card issuer receives your payment.
Different card issuers have different rules for determining when they charge interest. In general, once a card issuer begins to charge interest it will continue to do so until it receives your payment. This means that if you have been carrying a balance, you will be charged interest – sometimes called “residual interest” – from the time your bill was sent to you until the time your payment is received by your card issuer.
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 from your card issuer if it is not there.