Dennis particularly advises on fundamental rights within the EU, such as the right to free movement, and the prevention of tax avoidance. He is involved in numerous proceedings in the field of European tax law in different EU Member States and before the European Court of Justice.
Dennis is Professor of European Corporate Tax Law at the University of Amsterdam, with specialization in anti-BEPS rules. He is director of the Amsterdam Centre for Tax Law (ACTL). He has been guest lecturer at various domestic and foreign universities. Dennis also regularly contributes to various tax publications and has authored numerous articles on European tax law.