This book is the result of a research project entitled ??orizontal Tax Coordination within the EU and within States??that was conducted by the Institute for Austrian and International Tax Law at WU (Vienna University of Economics and Business). The aim of this project was to examine the role court judgments have played in the framework of tax harmonization in federal states and how decisive this impact was.rn rnIn this respect the participants took also a closer look at ECJ case law and how it may be compared to other jurisdictions where federal fiscal structures exist, such as the United States, Switzerland, Belgium, Spain, Austria, Russia, Mexico, Brazil, India and Australia. The judgments of the various courts were contrasted with each other in order to learn more about the impact on harmonization in the field of tax law. From these findings conclusions for the purpose of EU tax policy were drawn.