The EU filed charges against MasterCard on Thursday 9 July, accusing the company of raising the cost of card payments.
The union's antitrust regulator, the European Commission, is charging MasterCard because of high cross-border costs imposed on transfers within Europe as well as payments from and to non-EU countries.
"Many consumers use payment cards every day, when they shop for food, clothes or purchase anything online," Margrethe Vestagerthe, head of competition policy at the European Commission, said. "We currently suspect MasterCard is artificially raising the costs of card payments, which would harm consumers and retailers in the EU."
The charges are being imposed based on results of an investigation launched in 2013 into the card network.
The EU argues that the extra costs, mainly imposed on charges between banks and businesses, prevent retailers and other companies from taking advantage of lower fees offered at foreign banks.
MasterCard told Reuters: "We will be formally responding to the statement of objections and are also working with the European Commission on the issue as part of an ongoing constructive dialogue."
The charges, when confirmed, could be up to 10% of the company's $9.5bn (£6.17bn, €8.59bn) revenue. The commission is also investigating rival Visa for possible volatile charges.