This dissertation deals with the topic of of Book-Tax Conformity, i.e. the degree to which book and tax accounting should be aligned. The aim is to provide further evidence on the research question of the true effects and characteristics of one-book and two-book systems and their effects on firms reporting behavior as well as to derive propositions on the appropriate degree of book-tax conformity. In addition, supranational trends and economic influencing factors which might prospectively affect tax accounting and tax reporting (CCTB, Country-by-Country Reporting, low interest environment) should be further analyzed. The thesis consists of five self-contained papers