UK Opt-Out Class Actions – A New (Anti)Competitive Landscape

EXECUTIVE SUMMARY

On 11 December 2020, the UK Supreme Court handed down its highly anticipated judgment in the case of Mastercard v Merricks. The case concerned the certification procedure for US-style ‘opt-out' collective (class action) proceedings before the UK Competition Appeal Tribunal (the “CAT”). Opt-out actions automatically treat anyone who falls within the scope of the proposed class definition as being a member of the class unless they explicitly opt-out or withdraw. Opt-in actions, as the name suggests, require potential claimants to expressly sign up to be a member of the class.

The claim against Mastercard was brought by Mr Merricks as a follow-on damages claim (i.e., a claim based upon an existing decision in 2007 by the European Commission (the “Commission”) that Mastercard had breached EU competition laws in relation to the setting of interchange fees). Damages of c. £14 billion were sought on behalf of an opt-out class of some 46.2 million UK