The principle of the neutrality of VAT, as given specific definition by the case-law relating to Article 203 of Council Directive 2006/112/EC, must be interpreted as precluding a tax authority from refusing, on the basis of a provision of national law intended to transpose that article, the supplier of an exempt supply the refund of VAT invoiced in error to a customer on the ground that the supplier had not corrected the erroneous invoice, in circumstances where that authority had definitively refused the customer the right to deduct that VAT and such definitive refusal results in the system for correction provided for under national law no longer being applicable.
CJ 11 April 2013, nr. C-138/12