It follows from the foregoing that point 6 of Annex III to Directive 2006/112 as amended is not invalid on the ground that the legislative procedure that led to its adoption was vitiated by infringement of an essential procedural requirement.

Consequently, as the Court found in paragraph 53 of the judgment of 5 March 2015, Commission v Luxembourg ( C‑502/13 , EU:C:2015:143 ), the text of point 6 of Annex III to Directive 2006/112 as amended is nothing other than a simplification of the drafting of the text which was set out in the proposal for a directive and the substance of which has been fully preserved.

Given that that proposal indicated that it also covered books supplied on ‘any … physical support [similar]’ to printed books, audio books, CDs and CD-ROMs, the list in the proposal must be regarded as not being exhaustive, but as being intended to illustrate the fact that all feasible physical means of support were covered, in line with what the Council finally decided upon in point 6 of Annex III to Directive 2006/112 as amended.

Nonetheless, it cannot be concluded from those differences that point 6 of Annex III to Directive 2006/112 as amended differs in essence from the text that was set out in the proposal for a directive.

It is thus apparent on comparing the respective wording of the proposal for a directive and of point 6 of Annex III to Directive 2006/112 as amended that point 6 differs from the proposal inasmuch as it does not mention, as physical means of support that can give rise to the application of a reduced rate of VAT, ‘audio books, CDs [and] CD-ROMs’, which are listed by the proposal, or expressly relate, unlike the proposal, to books ‘that predominantly reproduce the same information content as printed books’, but makes reference to the supply of books on ‘all physical means of support’.

The obligation to consult the Parliament during the legislative procedure in the cases laid down by the Treaty means that the Parliament is consulted afresh whenever the text finally adopted, taken as a whole, differs in essence from the text on which the Parliament has already been consulted, except in cases where the amendments substantially correspond to a wish of the Parliament itself (see, to that effect, judgment of 5 October 1994, Germany v Council, C‑280/93 , EU:C:1994:367 , paragraph 38 and the case-law cited).

Examination of the questions referred for a preliminary ruling has disclosed no factor of such a kind as to affect the validity of point 6 of Annex III to Council Directive 2006/112/EC of 28 November 2006 on the common system of value added tax, as amended by Council Directive 2009/47/EC of 5 May 2009, or of Article 98(2) of that directive, read in conjunction with point 6 of Annex III thereto.

It should be recalled at the outset that the Court has consistently held that the principle of equal treatment requires that comparable situations must not be treated differently and different situations must not be treated in the same way unless such treatment is objectively justified (judgments of 12 November 2014, Guardian Industries and Guardian Europe v Commission, C‑580/12 P, EU:C:2014:2363, paragraph 51, and of 4 May 2016, Pillbox 38, C‑477/14, EU:C:2016:324, paragraph 35).

In accordance with settled case-law of the Court, the factors which distinguish different situations, and the question whether those situations are comparable, must be determined and assessed in the light of the subject matter of the provisions in question and of the aim pursued by them, whilst account must be taken for that purpose of the principles and objectives of the field in question (see, to that effect, judgment of 16 December 2008, Arcelor Atlantique et Lorraine and Others, C‑127/07, EU:C:2008:728, paragraph 26 and the case-law cited).

Consequently, it must be found that, in the light of the objective pursued by Article 98(2) of Directive 2006/112 as amended, read in conjunction with point 6 of Annex III thereto, the supply of digital books on all physical means of support and the supply of digital books electronically amount to comparable situations.

Therefore, since Article 98(2) of Directive 2006/112 as amended, read in conjunction with point 6 of Annex III thereto, has the effect of precluding the application of a reduced rate of VAT to the supply of digital books electronically although application of a reduced rate is permitted for the supply of digital books on all physical means of support, those provisions must be regarded as establishing a difference in treatment between two situations that are, however, comparable in the light of the objective pursued by the EU legislature.

Where a difference in treatment between two comparable situations is found, the principle of equal treatment is not infringed in so far as that difference is duly justified (see, to that effect, judgment of 16 December 2008, Arcelor Atlantique et Lorraine and Others, C‑127/07, EU:C:2008:728, paragraph 46).

That is the case, according to settled case-law of the Court, where the difference in treatment relates to a legally permitted objective pursued by the measure having the effect of giving rise to such a difference and is proportionate to that objective (see, to that effect, judgments of 17 October 2013, Schaible, C‑101/12, EU:C:2013:661, paragraph 77, and of 22 May 2014, Glatzel, C‑356/12, EU:C:2014:350, paragraph 43).

In that respect, it is understood that, when the EU legislature adopts a tax measure, it is called upon to make political, economic and social choices, and to rank divergent interests or to undertake complex assessments. Consequently, it should, in that context, be accorded a broad discretion, so that judicial review of compliance with the conditions set out in the previous paragraph of this judgment must be limited to review as to manifest error (see, to that effect, judgments of 10 December 2002, British American Tobacco (Investments) and Imperial Tobacco, C‑491/01, EU:C:2002:741, paragraph 123, and of 17 October 2013, Billerud Karlsborg and Billerud Skärblacka, C‑203/12, EU:C:2013:664, paragraph 35).

As the Council and the Commission explained in reply to a written question asked by the Court and at the hearing, the ruling out, in Article 98(2) of Directive 2006/112 as amended, of the application of a reduced rate of VAT to the supply of digital books electronically must be viewed as forming part of a specific VAT regime for e-commerce. It is apparent from their explanations that it was considered necessary to make electronically supplied services subject to clear, simple and uniform rules in order that the VAT rate applicable to those services may be established with certainty and, thus, that the administration of VAT by taxable persons and national tax authorities is facilitated.

Indeed, the principle of legal certainty, which underlies that objective, requires that EU rules enable those concerned to know unequivocally the extent of their rights and obligations so that they are in a position to order their affairs with the benefit of full information (see, to that effect, judgment of 15 July 2010, Commission v United Kingdom, C‑582/08, EU:C:2010:429, paragraph 49 and the case-law cited).

Furthermore, the Court has already acknowledged the legitimacy of the objective consisting in the laying down by a legislature of general rules which can be easily applied by economic operators and are easily verified by the competent national authorities (see, to that effect, judgment of 24 February 2015, Sopora, C‑512/13, EU:C:2015:108, paragraph 33).

To accept that the Member States are able to apply a reduced rate of VAT to the supply of digital books electronically, as is permitted for the supply of such books on all physical means of support, would effectively compromise the overall coherence of the measure intended by the EU legislature, consisting in the exclusion of all electronic services from the possibility of a reduced rate of VAT being applied.

Accordingly, the difference in treatment — resulting from Article 98(2) of Directive 2006/112 as amended, read in conjunction with point 6 of Annex III thereto — between the supply of digital books electronically and the supply of books on all physical means of support must be regarded as duly justified.

(see paras 41, 42, 49, 51-54, 57, 59, 60, 66, 70, 72, operative part)