Shoppers in 40 US states could see a surcharge of up to four per cent added to their credit card purchases from this week.
The new checkout fees are part of a multi-billion dollar class action settlement between retailers and Visa and MasterCard over credit card interchange fees.
The deal gives merchants the option to pass on the fee they are charged to process credit card payments to the consumer. The typical charge will be between 1.5% and three per cent of the purchase, with a four per cent cap.
Retailers who decide to add the charge are required to provide "clear disclosure" or signs in the store entrance, at the point of sale, on their Web site if it is an online purchase and on receipts.
The fees do not apply to debit cards and have also been deemed illegal in 10 states, including California and New York.
Even in states where the fees are legal, merchants are understood to be cautious about implementing them. The National Retail Federation - which was not part of the legal settlement - told NBC News that "not a single merchant we have spoken to plans to surcharge".
Acting on behalf of the financial services industry, the Electronic Payments Coalition has set up a Web page
devoted to the issue, which urges consumers to post messages on Twitter and Facebook decrying the move. A sample tweet helpfully provided by the EPC reads: WHAT?! Retailers can now charge a fee when we use credit cards! http://bit.ly/SorYVm #checkoutfees.