The hikes are set to come in October and April, with many of the rises targeting online transactions, says the Journal, citing sources and documents. Consulting firm CMSPI says the rises could add $502 million a year to merchant costs. In 2022, US merchants paid Visa and Mastercard $93 billion in credit card fees, according to the Nilson Report.Mastercard has disputed the WSJ report, claiming that "it is not correct"."We were clear on two points before the story was filed - there are no changes to Mastercard interchange rates and the one ’change’ referenced is an existing service we provide to acquirers, who can activate it as needed to drive a safer and more streamlined checkout experience for consumers," says a spokesman. "Our direct relationship is with the acquirer. And, it is the acquirer alone that determines how they price the service and connectivity they provide to their customer - the merchant. "Shares in both card giants rose by more than one per cent on the report.In March, a US federal appeals court upheld a $5.6 billion antitrust class-action settlement stretching back nearly 20 years between 12 million retailers and Visa and Mastercard over interchange fees.