Book excerpt: This book discusses the legal issues arising from the search for certainty in the relationship between Community law and direct tax law. In addition, it contains an in-depth analysis of the CILFIT doctrine in action and its demand for legal certainty. By looking at both how the case law of the European Court of Justice (ECJ) in the area of direct taxation fits the CILFIT criteria (ECJ, 6 October 1982, case 283/81, Srl CILFIT and Gavardo SpA), and how such criteria are complied with by national courts, the book reviews and discusses the application in the field of direct taxation of the criteria put forward by the ECJ. The book highlights some of the current challenges faced by the EU judicial system in view of the expansion of EU law and its decentralized application at national level.