In yet another indication of the inflationary effects of Brexit, Mastercard is preparing to at least quadruple the fees it charges to merchants located in the European Union and the rest of the European Economic Area when British cardholders buy their goods online. It warned that the move could lead to higher prices for consumers should the merchants decide to pass on the higher costs of e-commerce transactions. Mastercard said it will adapt the interchange rates on U.K. cards to the commitments it gave to the European Commission in 2019 for non-EEA card transactions. In practice, when a credit or debit card is used, merchants pay an interchange fee to the bank that issued the card. In an effort to reduce costs for both retailers and consumers and to help create an EU-wide payments market, the EU capped in 2015 the fees for the use of payment cards issued in the EEA at 0.3 percent for credit cards and 0.2 percent for debit cards. Mastercard has told retailers the rates will increase to 1.5 percent and 1.15 percent, respectively, in line with the ceiling the EU set on the use of non-EEA cards in 2019. Visa, which is subject to the same limits on interchange fees, has thus far failed to announce an increase in its fees. Should it decide to do so, Visa said it would seek to provide clients with advance notice so that they could plan ahead.