This article discusses the taxation of hidden reserves under the Commission’s Common Consolidated Corporate Tax Base (CCCTB) proposai. For fiscal reasons, the CCCTB regime should tax hidden reserves with regard to assets transferred between a non-group company and the group to avoid a tax-free cross-border transfer of hidden reserves. As a result, corporate share deals would be taxed that are currently tax exempt in most Member States. The author analyses this problem and highlights tax planning opportunities.