The Competition Appeal Tribunal (CAT) has granted certification for opt-out proceedings against Valve Corporation, alleging that approximately 14 million consumers have been overcharged for games and additional content on Steam, potentially amounting to £656 million. The claim accuses Valve of abusing market dominance through practices such as Platform Parity Obligations, Anti-steering and Tying Provisions, and excessive commission charges. Valve contested the certification, questioning the methodologies for establishing liability and loss, but the CAT dismissed these objections. The Tribunal examined the Class Representative’s funding arrangements and concluded that the claim is representative of a large group of consumers with moderate losses, aligning with the Supreme Court's description of a 'paradigm' case for opt-out certification. Legal representation for the Class Representative was provided by Milberg London LLP and the claim is financially supported by Bench Walk Advisors.