Not true since January. Part of a class-action settlement with Visa and MasterCard allows merchants to add a surcharge of up to 4% for paying with credit cards. The Dodd-Frank bill in 2010 banned prohibitions on the other terminology for the same thing -- cash discount. Cash discounts, credit surcharges, and minimums to pay with credit as low as $10 are all currently legal, and old merchant account agreement terms that prohibited them are void or unenforceable.