The rule change is part of the settlement in a class action antitrust lawsuit against Visa and MasterCard and some big banks that process credit card purchases.
But will many stores do this?
"We really are not expecting to see a flood of surcharges now," says Ruth Susswein is with a consumer group called Consumer Action. "But what we're saying is that consumers need to be aware that this can happen. And if it does happen you must be notified in advance."
A brick-and mortar-store must post a notice at the store's entrance. The exact percentage of the surcharge does not need to be disclosed until the point of sale. The receipt must list the amount of the surcharge.
Online stores with a surcharge don't need to alert shoppers until they reach the page where credit cards are first mentioned. In most cases, that means the final step of checkout when the purchase is being completed.
The surcharge can vary based on the type of credit card. For example, it could be higher for a rewards card or premier card. American Express does not allow merchants to charge customers a transaction fee. A fee for using a debit card is still prohibited.