The principles of fiscal neutrality, equal treatment and effectiveness do not preclude national legislation, such as that at issue in the main proceedings, which, in the context of the reduction of the limitation period, on the one hand, for claims for overpaid value added tax and, on the other hand, for claims for deduction of input value added tax, provides different transitional periods, with the result that claims relating to two accounting periods of three months are subject to different limitation periods depending on whether they concern the repayment of overpaid value added tax or the deduction of input value added tax.