Article 7 of Directive 2003/88/EC of the European Parliament and of the Council of 4 November 2003 concerning certain aspects of the organisation of working time and of Article 31(2) of the Charter of Fundamental Rights of the European Union must be interpreted as precluding national legislation, such as that at issue in the main proceedings, under which, in the event that the worker did not ask to exercise his right to paid annual leave during the reference period concerned, that worker loses, at the end of that period — automatically and without prior verification of whether the employer had in fact enabled him to exercise that right, in particular through the provision of sufficient information — the days of paid annual leave acquired under those provisions in respect of that period, and, accordingly, his right to an allowance in lieu of paid annual leave not taken in the event that the employment relationship is terminated. It is, in that regard, for the referring court to determine, taking into consideration the whole body of domestic law and applying the interpretative methods recognised by it, whether it can arrive at an interpretation of that right capable of ensuring the full effectiveness of EU law.

While it should be made clear in the response, in that regard, to the first question, that compliance with the requirement, for employers, under Article 7 of Directive 2003/88 should not extend to requiring employers to force their workers to actually exercise their right to paid annual leave (see, to that effect, judgment of 7 September 2006, Commission v United Kingdom, C‑484/04, EU:C:2006:526, paragraph 43), the fact remains that employers must, however, ensure that workers are in a position to exercise such a right (see, to that effect, judgment of 29 November 2017, King, C‑214/16, EU:C:2017:914, paragraph 63).

To that end, as the Advocate General also observed in points 41 to 43 of his Opinion, the employer is in particular required, in view of the mandatory nature of the entitlement to paid annual leave and in order to ensure the effectiveness of Article 7 of Directive 2003/88, to ensure, specifically and transparently, that the worker is actually in a position to take the paid annual leave to which he is entitled, by encouraging him, formally if need be, to do so, while informing him, accurately and in good time so as to ensure that that leave is still capable of ensuring for the person concerned the rest and relaxation to which it is supposed to contribute, that, if he does not take it, it will be lost at the end of the reference period or authorised carry-over period.

In addition, the burden of proof in that respect is on the employer (see, by analogy, judgment of 16 March 2006, Robinson-Steele and Others, C‑131/04 and C‑257/04, EU:C:2006:177, paragraph 68). Should the employer not be able to show that it has exercised all due diligence in order to enable the worker actually to take the paid annual leave to which he is entitled, it must be held that the loss of the right to such leave at the end of the authorised reference or carry-over period, and, in the event of the termination of the employment relationship, the corresponding absence of a payment of an allowance in lieu of annual leave not taken constitutes a failure to have regard, respectively, to Article 7(1) and Article 7(2) of Directive 2003/88.

Since the legislation at issue in the main proceedings is an implementation of Directive 2003/88, Article 31(2) of the Charter is intended to apply to the case in the main proceedings (see, by analogy, judgment of 15 January 2014, Association de médiation sociale, C‑176/12, EU:C:2014:2, paragraph 43).

In that context, it should, finally, be recalled that limitations may be imposed on the fundamental right to annual paid leave affirmed in Article 31(2) of the Charter only in compliance with the strict conditions laid down in Article 52(1) thereof and, in particular, the essential content of that right. Thus, Member States may not derogate from the principle flowing from Article 7 of Directive 2003/88 read in the light of Article 31(2) of the Charter, that the right to paid annual leave acquired cannot be lost at the end of the leave year and/or of a carry-over period fixed by national law, when the worker has been unable to take his leave (see, to that effect, judgment of 29 November 2017, King, C‑214/16, EU:C:2017:914, paragraph 56).

(see paras 44-46, 50, 54, 61, operative part1)