Art. 287, 3
The audit shall be based on records and, if necessary, performed on the spot in the other institutions of the Community, on the premises of any body which manages revenue or expenditure on behalf of the Community and in the Member States, including on the premises of any natural or legal person in receipt of payments from the budget. In the Member States the audit shall be carried out in liaison with national audit bodies or, if these do not have the necessary powers, with the competent national departments. The European Court of Auditors and the national audit bodies of the Member States shall cooperate in a spirit of trust while maintaining their independence. These bodies or departments shall inform the European Court of Auditors whether they intend to take part in the audit.
The other institutions of the Community, any bodies managing revenue or expenditure on behalf of the Community, any natural or legal person in receipt of payments from the budget, and the national audit bodies or, if these do not have the necessary powers, the competent national departments, shall forward to the European Court of Auditors, at its request, any document or information necessary to carry out its task. […]