This publication provides an overview of the EU rules on State aid. First, it looks at the notion of State aid - in particular, the conditions that must be satisfied for there to be aid under the EU regime. It then considers the mandatory and discretionary exemptions to the general prohibition on State aid, as well as the block exemptions, guidelines and frameworks for the application of State aid policy. It also explains the European Commission’s role in investigating State aid, the rules on recovery of unlawful aid and the role of the European and national courts in enforcing State aid rules. Finally, it considers the impact of Brexit on State aid rules as applicable to the UK.