Tax law The question of the harmonisation of VAT rates has been exercising minds for several years, and continues to raise serious, essentially budgetary, difficulties. 3. Harmonisation of direct taxation a) State aid The European Commission has also paid particular attention to the issue of State aid, looking through the optic of the Code of Conduct, in an attempt to bring an end to unfair tax competition within the European Union. b) Corporation tax base: the CCCTB project The European authorities are currently working on the introduction of a common consolidated corporate tax base (CCCTB). This project has been actively supported by Germany and France since it was launched in 2001. This work led to the presentation of a Proposal for a Directive on 16 March 2011 (COM(2011) 121/4). The common consolidated tax base is presented as a single set of rules by which to determine the taxable result that may be used by companies that carry on their business within the European Union; it is a question of ensuring that a company, or an eligible group of companies only has to abide by a single tax system within the European Union and not those of the different Member States in which the business is carried on. Only the principles behind the calculation of the tax base are referred to here. The harmonisation of the corporate tax rates that are applied to this base is not part of this project. c) "Cross-border compensation for loss" The European Commission published a communication on this subject on 19 December 2006, proposing a scheme that takes account of the case law of the Court of Justice (the case of Marks and Spencer particularly). 383