1. 

EU law — Direct effect — National taxes incompatible with EU law — Repayment — Procedures — Application of national law — Limits — Adherence to the principle of sincere cooperation — Introduction of restrictive procedural rules specifically applicable to the restitution of taxation declared to be contrary to EU law — Lawfulness — Verification a matter for the national court (Art. 4(3) TEU) (see paras 31, 52, operative part)

2. 

EU law — Direct effect — National taxes incompatible with EU law — Repayment — Procedures — Payment of interest for late payment — Application of national law — Limits — Observance of the principle of equivalence — Verification a matter for the national court (see paras 37, 38, 52, operative part)

3. 

EU law — Direct effect — National taxes incompatible with EU law — Repayment — Procedures — Application of national law — Limits — Observance of the principle of effectiveness — Repayment contingent on the existence of funds received from a tax — No possibility of enforcement — Unlawful (see paras 49, 50, 52, operative part)

1.

The principle of sincere cooperation must be interpreted as precluding a Member State from adopting provisions making repayment of a tax which has been held to be contrary to EU law by a judgment of the Court, or the incompatibility of which with EU law results from such a judgment, subject to conditions relating specifically to that tax which are less favourable than those that would have applied, in their absence, to such repayment; it is for the referring court to determine whether that principle has been complied with in the present case.

2.

The principle of equivalence must be interpreted as precluding a Member State from providing for procedural rules which are less favourable for actions based on an infringement of EU law than those applicable to similar actions based on an infringement of domestic law. It is for the referring court to carry out the necessary checks to ensure compliance with that principle so far as concerns the legislation applicable to the dispute pending before it.

3.

The principle of effectiveness must be interpreted as precluding a system of repayment of sums owed under EU law and the amount of which has been established by enforceable judicial decisions, such as the system at issue in the main proceedings, which provides for the repayment of such sums by instalments over five years and which makes the execution of such decisions contingent on the availability of funds received in respect of another tax, without the individual having the right to compel public authorities to fulfil their obligations if they do not do so voluntarily.