Dear Liz: I have had a certain credit card for over five years. I just received a letter stating that my interest rate was going to be raised from 10.24% to 12.24%. My FICO score is 819 and I have never had late payments on any of my cards. I called the issuer to complain about this change but they will not reduce the rate. The letter states that they obtained my FICO score of 819 from Experian and used the score to make the decision to raise my APR. They told me that they are raising rates across the board for customers with FICO scores over 800. Why are credit card companies allowed to do this? It is so unfair.

Answer: Credit card companies are no longer allowed to raise interest rates arbitrarily on individuals’ existing balances, as they could — and often did — before the Credit Card Accountability Responsibility and Disclosure (CARD) Act of 2009. Now card issuers are allowed to raise your interest rate on an existing balance only if you’re 60 days or more late with your payment, a promotional rate has expired or the index to which a variable-rate card is linked has gone up.

Credit card companies can, however, raise your interest rate going forward for pretty much any reason they want, and new balances will accrue at the higher rate. Also, the CARD Act’s restrictions apply only to consumer credit cards; business credit cards aren’t covered by the law.

Changeable rates are just one of the reasons why it’s not smart to carry credit card balances. Since you have high credit scores, though, it should be easy for you to find another card with a low promotional rate. Some cards now offer a 0% rate for 12, 15 or 18 months, although you’ll typically pay a balance transfer fee of around 3%. Sites such as CreditCards.com, NerdWallet and LowCards.com, among others, list these competitive offers.

Once you get the new card, you should work to pay off the entire balance before the promotional rate expires.