Claire Micheau & Alexander Rust 
State Aid and Tax Law [PDF ebook] 

Among the areas of incompatibility between EU law and national tax law, one of the more troublesome is the repayment obligation that can burden enterprises that have received advantages from State Aid deemed illegal by the Commission. The number of infringement proceedings against Member States for violation of the State Aid provisions is increasing, and as a result more and more taxpayers are exposed to severe financial risk.