The Supreme Court unanimously upheld the conclusion of the Court of Appeal that the multi-lateral interchange fees (MIFs) infringed EU antitrust rules by illegally restricting competition in the acquiring market.

The landmark ruling concludes several years of economic and legal battle over the rate of interchange fees set by Visa and Mastercard. Many of the UK’s biggest retailers have already lodged substantial claims against the global schemes, with Sainsbury’s et al. previously being awarded over £69 million at the Court of Appeal.

In announcing the judgement, Justice Nicholas Hamblen dismissed all grounds of appeal brought by the credit card companies, except one point over the degree of precision required to calculate loss, the so-called broad axe issue.

"The effect of the collective agreement to set the MIF is to fix a minimum price floor for the [merchant service charge]," Justice Hamblen said. "A significant portion of the [charge] is thereby immunized from competitive bargaining and is determined by collective agreement rather than by competition."

The judgement does not specify exactly how much the merchants are entitled to in repayment, but it is expected to pave the way for other cases to be brought to the commercial court.

Callum Godwin, chief of economist at payments consultancy CMSPI, states: "The merchants have succeeded on the major issues and it leaves very little room for manoeuvre for Visa and Mastercard. This is a resounding victory for the merchant community - retailers now have a fantastic opportunity to issue claims off the back of this ruling. Further, this ruling could have major ramifications worldwide"

CMSPI is currently supporting over 50 merchants in quantifying and progressing their claims.

Godwin estimates that the maximum pay-out for merchants could be €17bn if Visa and Mastercard fail to prove pass-through benefits. If European merchants then proceed, it could be as much as €68bn - representing the total Interchange paid since 2013.