It's always a good idea to pay your credit card bill on time, but now you could be facing higher costs if you don't.
The interest credit cards charge on balances, known as APR, has risen sharply this year.
That's according to a survey of 100 credit cards by creditcards.com.
The average interest rate is now just over 17%.
That means paying late, carrying a balance or taking out a cash advance is going to cost you more.
Most cards, though, haven't raised the other frees they charge and the total number of credit card fees is actually down.