As of today, the European Union has not developed a common system of rules applicable to the reimbursement of taxes levied contrary to EU law. Lack of legislative activities in this field is understandable. The EU does not wish to interfere with the procedural autonomy of its Member States.
The Court of Justice only requires the Member States to follow two basic principles when taxes levied contrary to EU law are reimbursed. The conditions of repayment of taxes levied contrary to EU law may not be less favourable than those relating to similar claims regarding national charges (principle of equivalence) and they may not be so framed as to render virtually impossible the exercise of rights conferred by EU law (principle of effectiveness).
The Court of Justice does not prevent a national legal system from disallowing the repayment of charges which have been unduly levied, where doing so would entail unjust enrichment of recipients. The author of this article analyses the content of the 'unjust enrichment' exception in the Court of Justice's case law, its current legal status and the position of this exception regarding the principles of equivalence and effectiveness.
The Court's approach towards 'unjust enrichment' is juxtaposed to its findings on the general principles of EU law. Emphasis is made on the primacy of EU law and the requirements of its effectiveness. The author tries to identify links between 'unjust enrichment' case law and the developing general principle of EU law - the prohibition of abuse.Intertax