This chapter gives an overview of UK competition law sanctions and their objectives, and provides a critical analysis of: the method for calculating fines; the Competition and Markets Authority (CMA)’s leniency and settlement policies; review by the appropriate court; private enforcement; the level of enforcement and compliance with UK competition law; and other sanctions against undertakings and individuals. The major issues in the UK centre on the comparatively low number of cases completed by the CMA and the potential chilling effect of its criminal cartel offence. Brexit creates new opportunities for the UK to design and apply its sanctions in a more effective way and outside of the constraints of EU Competition Law, but it also creates significant challenges – in particular in requiring the scaling-up of the CMA’s enforcement to include cases that were previously investigated by the European Commission on the UK’s behalf.