The maximum surcharge cap for online payments made with a credit card is typically 4 percent, as of September 2015. Merchants cannot impose surcharges on transactions paid by a debit or prepaid card. Merchants pass on some of the cost of credit card transactions to their customers through surcharge fees.
The two largest credit card companies Visa and Mastercard require merchants who impose surcharges on their credit cards to charge the lesser of either 4 percent or the merchant discount rate. Merchants need to fully disclose the surcharge rates and the dollar amounts at the point of sale and on the receipts. However, 10 states currently prohibit or curtail surcharging: California, Colorado, Connecticut, Florida and Kansas, as well as Maine, Massachusetts, Oklahoma, Texas and Utah.