Merchants have some latitude when they change the amount they run on your credit card, but they have to let you know what they are doing.

For instance, when you put your credit card into a gas pump, it will frequently run an initial authorization for a set amount. Once you’re done pumping gas, the merchant will issue the actual charge for the amount of gas that you buy.

Tips and gratuities work similarly, where the terminal runs a pre-authorization so that the merchant can add in the amount that you write. That final amount is the amount charged on your credit card.

Merchants can also change the amount charged with credit card surcharges, which began in 2013. For instance, if you buy a $100 item and the merchant has a 1.5 percent surcharge, it will charge a total of $101.50 to your credit card.

The merchant has to let you know that it is going to do this before issuing the charge – either through signs at the entrance to the store or at the register – and should include the surcharge on the receipt.

Bear in mind that if you’re not paying your credit card balances in full, and if you’re paying interest on your balance, the cumulative interest adds up. You’re going to owe more on your credit cards, which could show up as higher utilization when you check your credit report.

_{About the Author
Steve Lander has been a writer since 1996, with experience in the fields of financial services, real estate and technology. Lander holds a Bachelor of Arts in political science from Columbia University.}

_{This article is provided for general guidance and information. It is not intended as, nor should it be construed to be, legal, financial or other professional advice. Please consult with your attorney or financial advisor to discuss any legal or financial issues involved with credit decisions.}