The proposal for an EU-wide common consolidated corporate tax base (CCCTB) is almost as old as the hills. It first saw the light of day as part of the Ruding Report in 1992, but has been relaunched several times since then, most recently and with renewed vigour by the EU Commission in 2015.

There have been various variations of the basic proposal, but all incorporate a common tax base for the determination of corporate profits across the EU and a process for the division of that profit between EU member states by reference to some sort of formula. The most recent iteration included a proposal for mandatory adoption of CCCTB by multi-national enterprises (MNEs) and a formula for apportionment using three main factors: labour (payroll and head-count); sales; and capital.

Whereas in the past, the proposal for an EU-wide CCCTB was seen primarily as a simplification measure to enhance the operation of the Single Market, the most recent proposal has also been viewed as an important element in the EU's attempts to address cross-border tax planning by multi-national enterprises.

Previous attempts to introduce a CCCTB have floundered, in no small part, due to the staunch opposition of the UK government. Prior to the Brexit vote, the UK government stated its opposition to the most recent proposal. Following the Brexit referendum, the UK's imminent departure from the EU would appear to remove one of the CCCTB's most vociferous opponents and – unless other member states who oppose the CCCTB (such as Ireland) are prepared to block it – significantly increases the likelihood of the adoption of the CCCTB in the EU or at least by a material number of EU member states under the qualified majority voting procedure.

Even if the CCCTB proposal is ultimately adopted, it is not likely to stop tax planning or tax competition between EU member states: tax planning and tax competition will simply move to focus on the factors that form part of the formula for apportionment rather than on the factors that are taken into account in establishing taxable presence. In addition, while a CCCTB system will avoid the need for transfer pricing between EU member states, it will not overcome the need for MNEs properly to transfer price transactions between entities within the EU and those outside (including, in a post-Brexit world, the UK).