In Switzerland, certain taxpayers have the option to be taxed based on their expenses. Due to the steadily increasing number of individuals taxed at a flat rate and the resulting tax revenues, this taxation model is seen by its proponents as an effective tool in international tax competition and for generating non-fiscal benefits. Opponents view the expense-based taxation primarily as an unconstitutional and arbitrary privilege for wealthy foreign nationals. Consequently, flat-rate taxation is controversial domestically. However, there is little scientific basis for discussion on this topic. Andrea Stoffel analyzes the constitutionality and economic significance of expense-based taxation based on current doctrine and case law, as well as existing studies. The findings are supplemented by expert surveys.