After intensive and extensive preparation, the European Commission released the long-awaited proposal for a Council Directive on a Common Consolidated Corporate Tax Base (CCCTB) on 16 March 2011. In the context of the Europe 2020 Strategy, major objectives of the proposed CCCTB are the elimination of transfer pricing concerns, the removal of double taxation due to conflicting tax claims between Member States and, of course, the reduction of tax compliance costs. However, as the second and the third step of the proposed CCCTB, i.e. the consolidation and the allocation mechanism, still suffer from considerable shortcomings, we recommend introducing the CCCTB in two steps. In this context, our paper focuses on the first step of a CCCTB, i.e. the common corporate tax base (CCTB). The paper combines qualitative and quantitative analyses on the key differences and similarities between the proposed CCTB and current tax accounting practice in all 27 Member States, Switzerland and the United States It offers not only a broad geographical scope, but also great detail in analysing the differences in tax accounting and quantifying the change in tax burden induced by the introduction of a CCTB in each Member State, Switzerland and the United States.