The first and second questions
21 By its first and second questions, which it is appropriate to consider together, the referring court asks, in essence, whether the principle of the neutrality of VAT, as given specific definition by the case-law relating to Article 203 of Directive 2006/112, 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 incorrect 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.
22 In order to answer those questions, it should first be noted that Article 203 of Directive 2006/112 provides that any person who enters VAT on an invoice is liable to pay the tax entered on the invoice.
23 According to the case-law of the Court of Justice, those persons are liable to pay the VAT entered on an invoice independently of any obligation to pay it on account there being a transaction subject to VAT (see Case C-566/07 Stadeco [2009] ECR I-5295, paragraph 26 and the case-law cited, and Case C-642/11 Stroy trans [2013] ECR, paragraph 29).
24 In providing that the VAT entered on an invoice is payable, Article 203 of Directive 2006/112 seeks to eliminate the risk of loss of tax revenue which the right of deduction provided for in Article 167 et seq. of that directive might entail (see, to that effect, Stadeco, paragraph 28, and Stroy trans, paragraph 32). It is apparent from the order for reference that, since the tax authority had definitively refused the recipient of the invoice at issue the right of deduction, such a risk does not exist in the case in the main proceedings.
25 Secondly, as regards the refund of VAT invoiced in error, it should be noted that Directive 2006/112 does not contain any provisions relating to the adjustment, by the issuer of the invoice, of VAT that has been invoiced improperly and that, in those circumstances, it is in principle for the Member States to lay down the conditions in which improperly invoiced VAT may be adjusted (see, to that effect, Case C-454/98 Schmeink & Cofreth and Strobel [2000] ECR I-6973, paragraphs 48 and 49, and Stadeco, paragraph 35).
26 The Court has held that, in order to ensure the neutrality of VAT, it is for the Member States to provide, in their domestic legal systems, for the possibility of adjusting any tax improperly invoiced where the person who issued the invoice shows that he acted in good faith (see Case C-342/87 Genius [1989] ECR 4227, paragraph 18, and Stadeco, paragraph 36).
27 However, where the issuer of the invoice has, in sufficient time, wholly eliminated the risk of any loss of tax revenue, the principle of the neutrality of VAT requires that VAT which has been improperly invoiced can be corrected without such adjustment being made conditional by the Member States upon the good faith of the issuer of the relevant invoice. The adjustment cannot be dependent upon the discretion of the tax authority (see Schmeink & Cofreth and Strobel, paragraphs 58 and 68, and Stadeco, paragraphs 37 and 38).
28 Thirdly, it should be borne in mind that the Member States may indeed adopt measures in order to ensure the correct levying and collection of the tax and for the prevention of fraud (see Stadeco, paragraph 39). In particular, the condition that an incorrect invoice must be corrected before a refund of the VAT invoiced in error can be obtained can, in principle, ensure the elimination of the risk of loss of tax revenue (see Stadeco, paragraph 42).
29 None the less, the measures must not go further than is necessary to attain the objectives thereby pursued and may not, therefore, be used in such a way that they would have the effect of undermining the neutrality of VAT, which is a fundamental principle of the common system of VAT established by the relevant European Union law (see Stadeco, paragraph 39, and the case-law cited).
30 Consequently, if the refund of the VAT becomes impossible or excessively difficult as a result of the conditions under which applications for tax refunds may be made, the principle of neutrality and the principle of effectiveness may require that the Member States provide for the instruments and the detailed procedural rules necessary to enable the taxable person to recover the improperly invoiced tax (see Stadeco, paragraph 40, and the case-law cited).
31 With regard to the case in the main proceedings, it is apparent from the order for reference that Bulgarian law provides, in principle, for the possibility of obtaining a refund of VAT invoiced in error, but makes the exercise of that right conditional on the prior correction of the incorrect invoice. As pointed out in paragraph 28 of this judgment, such a requirement can ensure the elimination of the risk of loss of tax revenue.
32 However, it is also apparent from the order for reference that, pursuant to applicable national law, once the tax authority had definitively refused the recipient of the invoice the right to deduct the amount of VAT entered on it, the possibility of correcting the invoice at issue was no longer available to Rusedespred.
33 Furthermore, as the referring court observes, since the tax authority had definitively refused the recipient of the invoice at issue the right of deduction, the risk of loss of tax linked to the exercise of the right was completely eliminated.
34 In such circumstances, it must be held that making the adjustment of the VAT entered in error on an invoice subject to the condition that that invoice be corrected, a condition that is impossible to satisfy, goes further than is necessary to achieve the objective pursued by Article 203 of Directive 2006/112 of eliminating the risk of loss of tax revenue.
35 In the light of all of the foregoing, the answer to the first and second questions is that the principle of the neutrality of VAT, as given specific definition by the case-law relating to Article 203 of Directive 2006/112, 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 incorrect 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.
The third question
36 By its third question, the referring court asks, in essence, whether the principle of the neutrality of VAT, as given specific definition by the case-law relating to Article 203 of Directive 2006/112, may be relied on by a taxable person in order to contest a provision of national law that makes the refund of VAT invoiced in error conditional on the correction of the incorrect invoice, in circumstances where the right to deduct that VAT has definitively been refused and such definitive refusal results in the system for correction provided for under national law no longer being applicable.
37 A preliminary point to note is that the Court has consistently held that when national courts apply domestic law they are bound to interpret that law, so far as possible, in the light of the wording and the purpose of the directive concerned in order to achieve the result sought by the directive and, consequently, comply with the third paragraph of Article 288 TFEU. This obligation to interpret national law in conformity with European Union law is inherent in the system of the Treaty on the Functioning of the European Union, since it permits national courts, for the matters within their jurisdiction, to ensure the full effectiveness of European Union law when they determine the disputes before them (see, inter alia, Case C-282/10 Dominguez [2012] ECR, paragraph 24, and the case-law cited).
38 So far as concerns the possibility of relying on the principle of the neutrality of VAT against a Member State, it must be noted, first of all, that that principle is a fundamental principle of the common system of VAT as governed, inter alia, by Directive 2006/112 (see to that effect, inter alia, Stadeco, paragraph 39, and the case-law cited).
39 Secondly, as is apparent from paragraph 35 of this judgment, the principle of the neutrality of VAT, as given specific definition by the case-law relating to Article 203 of Directive 2006/112, must be interpreted as precluding a tax authority from refusing 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 incorrect 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.
40 According to case-law, the principle of the neutrality of VAT may, if necessary, be relied on by a taxable person against a provision of national law, or the application thereof, which fails to have regard to that principle (see, to that effect, Case C-306/06 Marks & Spencer [2008] ECR I-2283, paragraph 34). In circumstances such as those set out in paragraph 35 of this judgment, since the principle of the neutrality of VAT, as given specific definition by the case-law relating to Article 203 of Directive 2006/112, places an unconditional and sufficiently precise obligation on the Member State concerned, it may be relied on against a provision of national law that fails to have regard to that principle.
41 In the light of the foregoing, the answer to the third question is that the principle of the neutrality of VAT, as given specific definition by the case-law relating to Article 203 of Directive 2006/112, may be relied on by a taxable person in order to contest a provision of national law that makes the refund of VAT invoiced in error conditional on the correction of the incorrect invoice, in circumstances where the right to deduct that VAT has definitively been refused and such definitive refusal results in the system for correction provided for under national law no longer being applicable.