This article reviews the situations in which the incompatibility of a national tax with EU law can be established, and the ECJ's case law regarding the procedural time limits within which a taxpayer may seek reimbursement of a tax he previously paid which later turns out to be incompatible with EU law. It also examines the changes brought about by the ECJ's judgements in Kühne & Heitz (13 January 2004) and Weber's Wine World (2 October 2003).