The work addresses the question of why there is a sales tax and how it can be justified. In this context, it examines its compatibility with the fundamental rights of German constitutional law, as well as the connections with the fundamental rights guarantees of European law. The central legally binding guidelines are elaborated, within which a systematically designed sales tax must be maintained, along with practical suggestions for the national legislator. Furthermore, the future of sales taxation in the European Union is outlined, and potential solutions for the community legislator are presented. In this regard, the work aims to contribute to the necessary national and European reform of sales taxation.