This paper evaluates the Common Consolidated Corporate Tax Base (CCCTB) recently proposed by the European Commission. We find that if the CCCTB is introduced as it is currently proposed (including loss consolidation), then it is likely to impose large tax revenue costs of about one fifth of the corporate tax base. Second, we show that an application of the CCCTB proposals at only the European Union (EU) level would overlook the extent of profit shifting out of the EU and could lock in further unnecessary revenue losses. Third, major EU profit-shifting countries such as Luxembourg, Ireland and the Netherlands may experience significant revenue losses. Based on our analysis, the main policy recommendation is to consider extending the approach...