The UK government is proposing to further encourage private actions as a complement to the existing public enforcement regime. Its four main proposals are: to make the Competition Appeal Tribunal a ‘major’ venue for competition actions; to introduce a regime for opt-out collective actions for competition law; to promote alternative dispute resolution mechanism; and to protect the incentives for companies to expose cartels. In this response, Oxera focuses on the first of these—in particular, the proposed introduction of a rebuttable presumption on cartel overcharges that would be used in cases before the CAT (and other courts). Oxera notes that private actions face many obstacles, legal and procedural, and that the UK goverment’s initiative could contribute to removing these, but advises against the use of a rebuttable presumption on cartel overcharges.