BX v État belge (C-150/25)

Contents

Judgment of the Court (Fifth Chamber)12 March 2026^note(Reference for a preliminary ruling — Article 45 TFEU — Freedom of movement for workers — Income tax — Employment income received in another Member State — Exemption with progression in the Member State of residence — Failure to apply a bilateral convention for the avoidance of double taxation by a contracting State — Loss of part of the tax advantages relating to the personal and family circumstances of the taxpayer)In Case C‑150/25 [Marhaux],^noteREQUEST for a preliminary ruling under Article 267 TFEU from the tribunal de première instance du Luxembourg (Court of First Instance of Luxembourg, Belgium), made by decision of 19 February 2025, received at the Court on 20 February 2025, in the proceedingsBXvÉtat belge,THE COURT (Fifth Chamber),composed of M.L. Arastey Sahún, President of the Chamber, J. Passer, E. Regan (Rapporteur), D. Gratsias and B. Smulders, Judges,Advocate General: T. Ćapeta,Registrar: A. Calot Escobar,having regard to the written procedure,after considering the observations submitted on behalf of:– BX, by M. Igalson and M. Shooshtari, avocats,– the Belgian Government, by S. Baeyens, P. Cottin and C. Pochet, acting as Agents,– the French Government, by B. Dourthe and O. Duprat‑Mazaré, acting as Agents,– the European Commission, by M. Herold and W. Roels, acting as Agents,having decided, after hearing the Advocate General, to proceed to judgment without an Opinion,gives the following

Judgment

1This request for a preliminary ruling concerns the interpretation of Article 45 TFEU.

2The request has been made in proceedings between BX, on the one hand, a tax resident in Belgium, who receives employment income from Belgian, Luxembourg and French sources, and, on the other, the Belgian State concerning the lack of a deduction in respect of certain family expenses from the tax base for personal income tax in Belgium.

Legal context

The FEU Treaty

3Article 45 TFEU provides:1. Freedom of movement for workers shall be secured within the [European] Union.2. Such freedom of movement shall entail the abolition of any discrimination based on nationality between workers of the Member States as regards employment, remuneration and other conditions of work and employment.…4. The provisions of this Article shall not apply to employment in the public service.’

The Belgium-France Tax Convention

4The convention entre la France et la Belgique tendant à éviter les doubles impositions et à établir des règles d’assistance administrative et juridique réciproques en matière d’impôts sur les revenus, du 10 mars 1964 (Convention between France and Belgium seeking to avoid double taxation and to establish mutual administrative and legal rules of assistance in the field of income tax, of 10 March 1964; ‘the Belgium-France Tax Convention’), in the version in force at the time of the facts of the dispute in the main proceedings, provides in Article 10(1) thereof:‘Remuneration granted in the form of salaries, wages, pay, account balances and allowances by one of the Contracting States or by a legal person governed by public law of that State which is not carrying on an industrial or commercial activity shall be exclusively taxable in that State.’

5Article 25 of that convention is worded as follows:1.(a) Nationals of a Contracting State shall not be subjected in the other Contracting State to any taxation or any obligation connected therewith, which is other or more burdensome than the taxation and connected obligations to which nationals of that other State in the same situation, in particular with respect to residence, are or may be subjected. This provision shall also apply, notwithstanding the provisions of Article 1, to persons who are not residents of a Contracting State or of both Contracting States.(b) It is understood that a natural or legal person, a partnership or an association which is a resident of a Contracting State is not in the same situation as a natural or legal person, a partnership or an association which is not a resident of that State, irrespective of the definition of nationality, even if legal persons, partnerships and associations are regarded as nationals of the Contracting State of which they are residents.2. Notwithstanding the provisions of paragraph 1, natural persons who are residents of a Contracting State and are in salaried employment in the other Contracting State shall not be subjected in that other State, in respect of the income from that employment, to any taxation or connected obligation that is more burdensome than those to which natural persons who are residents of that other State and are in salaried employment in that State are or may be subjected. Nevertheless, personal deductions, allowances and tax reductions based on family circumstances or expenses that are granted by that other State to its own residents shall be reduced in proportion to the ratio which the earnings originating from that other State bear to the total earned income, irrespective of that income’s origin, that that resident receives.…4.“National” means, for each Contracting State:(a) all natural persons possessing the nationality of that State;(b) all legal persons, partnerships and associations formed in accordance with the legislation of that State.’

Belgian law

6Article 104 of the code des impôts sur les revenus 1992 (Income Tax Code 1992), in the version presented by the referring court as being that applicable to the dispute in the main proceedings, provides:‘The following expenditure shall be deducted from the total net income, in so far as it was actually paid during the tax period:1° 80% of the maintenance payments duly paid by the taxpayer to persons who are not part of his or her household, where they are paid to them in performance of an obligation arising from the Civil Code or the Judicial Code or from a similar legal obligation under foreign legislation, and 80% of the capital sums in lieu of such payments. …’

7The first paragraph of Article 155 of that code states:‘Income exempted under international conventions for the avoidance of double taxation shall be taken into account for the purpose of calculating tax, but the tax shall be reduced according to the proportion of the overall income represented by the exempted income.’

8Circular No Ci.RH.331/575.420 (AFER 8/2008), of 12 March 2008, provides:‘I. Introduction1. In the Belgian tax system, tax advantages relating to the personal and family circumstances of the taxpayer (deduction of maintenance payments, offsetting of the supplementary tax-free allowances for dependent children and so forth) are applied both to Belgian income and to foreign income. If the personal and family circumstances at issue have not been taken into account abroad, a part of those advantages is lost.The Netherlands applied a system of exemption with progression similar to that practised in Belgium. In its judgment [of 12 December 2002, de Groot (C‑385/00, EU:C:2002:750), concerning a] resident of the Netherlands, the Court of Justice of the European Communities held, however, that that practice was contrary to the legislation on the free movement of persons in the [European Union].Belgium was requested by the European Commission to bring the Belgian tax provisions relating to the application of the system of exemption with progression in the context “of the taxation of the income of natural persons”, into conformity with the obligations under [Articles 21, 45, 49 and 63 TFEU] and Articles 28, 31 and 40 of the [European Economic Area (EEA) Agreement of 2 May 1992 (OJ 1994 L 1, p. 3)].The following approach has been adopted: in cases where the personal and family circumstances of the taxpayer have not been taken into account abroad, a reduction in tax for income earned abroad will be granted in addition to the reduction provided for under [Article 155 of the Income Tax Code 1992].…II. Conditions under which applicable…9. Under no circumstances may the additional reduction be granted:– Where the advantages linked to personal or family circumstances have been granted to the taxpayer in the foreign [European Economic Area (EEA)] Member State(s) applying an apportionment rule. That is the case, in particular, where those advantages are granted in proportion to the income earned in the States at issue from worldwide income or total employment income. Such an apportionment rule is provided for by conventions for the avoidance of double taxation concluded with France (only in respect of certain categories of employment income) and the Netherlands …’

French law

9The code général des impôts (General Tax Code), in the version presented by the referring court as being that applicable to the dispute in the main proceedings (‘the general tax code’), provides, in Article 156 thereof:‘Income tax shall be assessed on the total annual net income available to each tax household. That net income shall be determined having regard to the properties and capital held by the members of the tax household referred to in Article 6(1) and (3), the professions which they pursue, their salaries, wages, allowances and life annuities and the profits from any business in which they engage, subject to deduction of:…II. The following expenses, where they are not taken into account in the assessment of the income of the different categories:…2° … maintenance payments satisfying the conditions laid down by Articles 205 to 211, 367 and 767 of the Civil Code with the exception of those paid to relatives in the ascending line where the provisions provided for in Article 199sexdecies(1) and (2) are applied; …’

10Article 164 A of the general tax code states:‘The French source income of persons who are not resident for tax purposes in France shall be determined in accordance with the rules applicable to similar income earned by the persons who are resident for tax purposes in France. However, none of the expenses deductible from total income pursuant to the provisions of this Code may be deducted.’

11Article 197 A of the general tax code provides:‘The rules of Article 197(I)(1) and (2) shall apply for the purpose of calculating the income tax payable by persons who, while not resident for tax purposes in France:a. Receive income from French sources; the tax may not, in that case, be less than an amount calculated by applying a rate of 20% to the fraction of the net taxable income which is lower than or equal to the upper limit of the second band of the income tax scale and a rate of 30% to the fraction above that limit; …b. By derogation from Article 164 A, in respect of the calculation of the rate of French tax on the total worldwide income provided for in point (a) of the present article, the maintenance payments provided for in Article 156(II)(2) shall be deductible subject to the same conditions and limits, where those payments are taxable in the hands of their beneficiary in France and taking them into account is not such as to understate the tax payable by the taxpayer in his or her State of residence.’

The dispute in the main proceedings and the question referred for a preliminary ruling

12BX is resident in Belgium for tax purposes and receives remuneration there in his capacity as director of an undertaking. In addition, he carries out employment activities in Luxembourg and France and receives income in respect of such activities in those countries. The French-source income consists of the salary of a civil servant, BX being an associate professor of universities in that country.

13In accordance with the Belgium-France Tax Convention, that French source income is taxed in France and exempt from personal income tax in Belgium, where it is, however, taken into account, after applying a tax scale by income band, in order to determine the tax, which is then reduced by the fraction of the tax calculated on the part of the exempt income.

14BX pays maintenance payments, referred to in French law as ‘pensions alimentaires’, to his daughter and former spouse, who reside in Belgium. He submitted, in respect of the 2020 and 2021 tax years, personal income tax returns in Belgium and referred, in those tax returns, to all of his income and the maintenance payments made.

15When determining the amount of tax payable by BX in respect of each of those tax years, the Belgian tax authorities granted BX the deduction of the maintenance payments made only in proportion to his Belgian-source income.

16Since his initial complaints did not lead to the annulment of or tax relief for the personal income tax assessments drawn up in respect of the 2020 and 2021 tax years, BX brought an action before the tribunal de première instance du Luxembourg (Court of First Instance of Luxembourg, Belgium), which is the referring court, claiming that the rule on the proportionate allocation of the deductible maintenance payments between the Belgian-source income and the foreign-source income, exempt from that tax, is contrary to Article 45 TFEU.

17The referring court considers that, under the Belgium-France Tax Convention, the French tax administration should have allowed BX to deduct from his taxable income in France part of the maintenance payments which he pays to his daughter and former spouse, but that, in fact, that Member State refuses such a deduction where the recipients of the maintenance payments, as is the case with those recipients, are not subject to the French tax system. In that context, that court expresses doubts as to the compatibility with Article 45 TFEU of the Belgian tax rules. Those rules result in a taxpayer receiving French-source income, but exempt from personal income tax under the Belgium-France Tax Convention, not being able to deduct part of the maintenance payments he or she pays from his or her taxable income in Belgium, without that part being taken into account in France in respect of his or her family circumstances in proportion to the income taxable in the latter Member State, on account of what the referring court considers to be a misapplication of that convention by the French tax administration.

18As regards the Luxembourg-source income received by BX, the referring court notes that BX also did not benefit in Luxembourg from tax advantages relating to his personal and family circumstances, but considers that it is in a position to apply the legislation in force, without the need to seek an interpretation that should be given by the Court, in that situation, of Article 45 TFEU.

19In those circumstances, the tribunal de première instance du Luxembourg (Court of First Instance of Luxembourg) decided to stay the proceedings and to refer the following question to the Court of Justice for a preliminary ruling:‘Must Article 45 TFEU be interpreted as meaning that a Member State ([the Kingdom of] Belgium) must take account, in calculating the tax to be paid by a natural person who is its resident, of the fact that, notwithstanding a non-discrimination provision of an international agreement – such as Article 25(2) of the [Belgium-France Tax Convention], which provides for personal deductions, allowances and tax reductions based on family circumstances or responsibilities being granted pro rata to non-residents – that person, on account of specific conditions laid down by the national legislation of the Member State of employment ([the French Republic]) – in the present case [Article 197 A] of the [c]ode général des impôts ([General Tax Code]), pursuant to which, for the calculation of French tax, maintenance payments [made by] that non-resident of that State of employment are not to be deducted for the purpose of calculating the rate of French tax unless those maintenance payments are taxable in the hands of their beneficiary in France and taking them into account is not such as to reduce the tax payable by the taxpayer in his or her State of residence – does not have the benefit of the maintenance payments being taken into account for tax purposes in proportion to the respective taxable income, either in the State of employment ([the French Republic]) or in the State of residence ([the Kingdom of] Belgium), even though that State of residence is able to calculate the tax by attributing the deductible maintenance payments to the local income after having excluded the part of the earnings that are exempted by international agreement, so as not to curtail the benefit of the deduction by attributing the maintenance payments to income which is exempted by international agreement subject to the method of exemption with progression and in respect of which that person has not actually had the benefit, in the State of employment, of those maintenance payments being taken into account proportionately?’

Consideration of the question referred

Jurisdiction of the Court and admissibility of the question

20In its written observations, the French Government submits that the reference for a preliminary ruling is inadmissible on the ground that, first of all, the referring court asks the Court to rule on the consequences of a possible infringement of a provision of a tax convention by one of the Contracting States, which does not fall within the jurisdiction of the Court. Next, that court did not sufficiently submit the legal and factual context of the dispute in the main proceedings. Lastly, in essence, the question referred is hypothetical. Article 25 of the Belgium-France Tax Convention is not applicable to that dispute by virtue of paragraph 2 of that Article 25, which limits, in respect of non-resident natural persons, the benefit of the non-discrimination rule which it lays down solely for persons employed in the other Contracting State. BX is not employed in France, since his employment relationship is of a statutory and non-contractual nature.

21In those respects, it should be noted, in the first place, that, where a request exceeds the limits, defined in the first paragraph of Article 267 TFEU, of what constitutes the possible subject matter of a reference for a preliminary ruling, it must be rejected not as inadmissible, but on account of the Court’s lack of jurisdiction (see, to that effect, order of 28 April 2025, A.En. Slovensko, C‑201/24, EU:C:2025:288, paragraphs 35 to 39).

22In accordance with those limits, the Court does not have jurisdiction to rule on a possible infringement, by a Member State, of provisions of a convention entered into by one or more other Member States designed to eliminate or to mitigate the negative effects of the coexistence of national tax regimes (judgment of 16 July 2009, Damseaux, C‑128/08, EU:C:2009:471, paragraph 22). Nor does the Court have jurisdiction to examine the relationship between a national measure and the provisions of a double taxation convention adopted for the avoidance of double taxation, since that question does not fall within the scope of the interpretation of EU law (judgment of 24 October 2018, Sauvage and Lejeune, C‑602/17, EU:C:2018:856, paragraph 17).

23That said, the fact remains that, in the context of the procedure provided for in Article 267 TFEU, the Court has jurisdiction to give a preliminary ruling on the interpretation of a provision of EU law in the light of the factual and legal situation described by the referring court in its request.

24Thus, where a referring court mentions the existence of a convention for the avoidance of double taxation as an element of the relevant legislative context, the Court must take that convention into account and the referring court’s interpretation of it, in order to provide that court with an interpretation of EU law which will be of use to it (see, to that effect, judgment of 24 October 2018, Sauvage and Lejeune, C‑602/17, EU:C:2018:856, paragraph 18).

25It follows that, even if, in the present case, the only question referred for a preliminary ruling is based on a premiss linked to the referring court’s interpretation of the Belgium-France Tax Convention, it is not appropriate to find that the Court lacks jurisdiction given that that question concerns the interpretation of Article 45 TFEU and not the interpretation of that convention. By contrast, the answer that the Court will be required to give to that question will be subject to that premiss being correct, which it is for the referring court to determine.

26As regards, in the second place, the admissibility of the request for a preliminary ruling, it should be recalled that, in accordance with settled case-law, the questions on the interpretation of EU law referred by a national court in the factual and legislative context which that court is responsible for defining, and the accuracy of which is not a matter for the Court to determine, enjoy a presumption of relevance. The Court may refuse to rule on a question referred for a preliminary ruling from a national court only where it is quite obvious that the interpretation of EU law sought bears no relation to the actual facts of the main action or its purpose, where the problem is hypothetical, or where the Court does not have before it the factual or legal material necessary to give a useful answer to the questions submitted to it (judgment of 18 June 2024, Bundesrepublik Deutschland (Effect of a decision granting refugee status), C‑753/22, EU:C:2024:524, paragraph 44).

27In particular, as regards the latter situation, according to settled case-law, reflected in Article 94(a) and (b) of the Rules of Procedure of the Court of Justice, the need to provide an interpretation of EU law which will be of use to the national court makes it necessary, in particular, for that court to, first, set out the relevant facts or provide, at least, an account of the facts on which the questions are based, second, define the legislative context of the questions it is asking (see, to that effect, judgment of 30 October 2025, Attal et Associés, C‑321/24, EU:C:2025:836, paragraph 20 and the case-law cited).

28In the present case, the referring court has set out in sufficient detail the relevant factual and legislative context of the dispute in the main proceedings for the Court to answer the question referred in a manner which may be useful to that court. In addition, even though it is not for the Court, in the context of the procedure laid down in Article 267 TFEU, to rule on whether the referring court’s interpretation of the Belgium-France Tax Convention or French law is correct, since, in the context of that procedure, which is based on a clear separation of functions between the national courts and the Court, any assessment of the facts and of national law, with which the conventions concluded between two Member States must be equiparated, is a matter for the national court alone, it is not obvious from the documents before the Court that the question referred bears no relation to the actual facts of the main action or its purpose or that it raises a hypothetical problem.

29Consequently, it is not appropriate to declare the request for a preliminary ruling to be inadmissible.

Substance

30By its question, the referring court asks, in essence, whether Article 45 TFEU must be interpreted as precluding national legislation the application of which leads to the loss in part of the benefit of a tax deduction designed to take account of the personal and family circumstances of resident taxpayers in one Member State, where they receive employment income in a second Member State, which is exempt from tax in the Member State of residence under a bilateral tax convention, whereas resident taxpayers who have no income from another Member State wholly benefit from that deduction, where, under that bilateral tax convention, the loss of that part of that deduction should have been offset, in the second Member State, by the corresponding opportunity to obtain a similar deduction, in proportion to the income received in the second Member State.

31In that regard, it should be recalled that under Article 45 TFEU, the freedom of movement for workers is to be secured within the European Union. According to paragraph 2 of that Article 45, that freedom of moment is to entail the abolition of any discrimination based on nationality between workers of the Member States as regards employment, remuneration and other conditions of work and employment.

32It is true that Article 45(4) TFEU states that the provisions set out in paragraphs 1 to 3 of that article are not to apply to employment in the public service. In the case at issue in the main proceedings, the income received by BX in a Member State other than that of his residence consists of a salary as a civil servant.

33However, that provision cannot have a scope going beyond the aim in view of which it was adopted, which is to allow Member States to restrict the admission of foreign nationals to certain posts in the public service, but not to authorise those Member States to adopt discriminatory measures with regard to remuneration or other conditions of employment against nationals of other Member States who have been admitted to such employment (see, to that effect, judgment of 12 February 1974, Sotgiu, 152/73, EU:C:1974:13, paragraph 4).

34Accordingly, Article 45(4) TFEU must be interpreted as merely depriving a worker of the application of the provisions contained in paragraphs 1 and 2 of Article 45 TFEU only as regards access to certain posts in the public service.

35By contrast, that provision does not preclude, in a dispute involving tax matters, a resident taxpayer who is employed in the public service in another Member State from being able to rely on the status of ‘worker’, within the meaning of Article 45 TFEU, as regards the taxation of his or her income generated by that employment.

36That said, it must also be borne in mind that, as EU law currently stands, each Member State remains free to organise, in compliance with that law, its system of taxation of income, with the result that the freedoms of movement cannot be understood as meaning that a Member State is required to draw up its tax rules on the basis of those in another Member State in order to ensure, in all circumstances, taxation which removes any disparities arising from national tax rules (see, to that effect, judgments of 27 February 2020, AURES Holdings, C‑405/18, EU:C:2020:127, paragraph 32, and of 10 November 2022, VP Capital, C‑414/21, EU:C:2022:871, paragraph 19).

37In particular, according to settled case-law, the disadvantages that may result from the parallel exercise of the tax powers of the various Member States, such as double taxation, do not constitute restrictions prohibited by the FEU Treaty, in so far as such an exercise is not discriminatory (see, in particular, judgment of 25 February 2021, Société Générale, C‑403/19, EU:C:2021:136, paragraph 28 and the case-law cited).

38Discrimination can arise only through the application of different rules to comparable situations or the application of the same rule to different situations (see, in particular, judgments of 14 February 1995, Schumacker, C‑279/93, EU:C:1995:11, paragraph 30; of 18 June 2015, Kieback, C‑9/14, EU:C:2015:406, paragraph 21; and of 9 February 2017, X, C‑283/15, EU:C:2017:102, paragraph 29).

39Accordingly, the comparability of a cross-border situation with an internal one must be examined having regard to the purpose, content and aims pursued by the rules at issue (see, to that effect, judgments of 13 November 2019, College Pension Plan of British Columbia, C‑641/17, EU:C:2019:960, paragraph 65 and the case-law cited, and of 30 January 2020, Köln-Aktienfonds Deka, C‑156/17, EU:C:2020:51, paragraph 76).

40Thus, where national rules provide, in order to take account of the personal and family circumstances of taxpayers, for deductions applicable, in the calculation of the tax base, to the total income, resident and non-resident taxpayers must be regarded, as a general rule, as not being in comparable situations, in so far as the income received in the territory of a State by non-resident taxpayers, income which is, in principle, the only income taxed, constitutes, most often, only a part of the overall income of those taxpayers (see, to that effect, judgment of 14 February 1995, Schumacker, C‑279/93, EU:C:1995:31, paragraphs 31 and 32).

41By contrast, where a Member State applies a principle of taxation, at the place of residence, to the total income of the taxpayers, including that from a foreign source, the resident taxpayers who have such foreign-source income as a result of exercising their right to freedom of movement for workers and those who do not have such income must be regarded as being in comparable situations.

42Having regard to that comparability of the situations of the different categories of resident taxpayers where the Member State of residence exercises its powers of taxation with regard to the total income of such taxpayers, it is, in principle, for that Member State to grant to those different categories of resident taxpayers all the tax advantages relating to their personal and family circumstances, even if those taxpayers have income from a foreign source, that same Member State being, moreover, without exception, best placed to assess the personal ability of those taxpayers to pay tax, resulting from the taking into account of their total income and their personal and family circumstances, since that is where, also in principle, the personal, family and financial interests of those taxpayers are centred (see, to that effect, judgments of 14 February 1995, Schumacker, C‑279/93, EU:C:1995:31, paragraphs 32 and 33, and of 12 December 2013, Imfeld and Garcet, C‑303/12, EU:C:2013:822, paragraph 43).

43The Court has, however, accepted that, in the absence of harmonising measures adopted at EU level, the Member States remain free to alter, by way of bilateral or multilateral agreements for the avoidance of double taxation, that correlation between the total income of residents and residents’ general personal and family circumstances to be taken into account by a Member State of residence. A Member State of residence applying a principle of taxation, at the place of residence, to the total income of taxpayers can therefore be released by way of an international agreement from its obligation to take into account in full the personal and family circumstances of taxpayers residing in its territory who work at least in part in another Member State if, by way of exception, particularly in light of the fact that the conventions of that nature take precedence over the legislation laying down such a principle, it exempts from tax the income from the Member State with which it has ratified such a convention (see, to that effect, judgments of 12 December 2002, de Groot, C‑385/00, EU:C:2002:750, paragraph 99, and of 15 July 2021, État belge (Loss of tax advantages in Member State of residence), C‑241/20, EU:C:2021:605, paragraph 44).

44However, in that situation, that Member State of residence cannot be released from its obligation to take into account in full the personal and family circumstances of those resident taxpayers who work at least in part in another Member State unless, in the light of all the tax advantages relating to their personal and family circumstances thus granted, those circumstances are taken into account in full (see, to that effect, judgments of 12 December 2002, de Groot, C‑385/00, EU:C:2002:750, paragraphs 100 and 101, and of 15 July 2021, État belge (Loss of tax advantages in Member State of residence), C‑241/20, EU:C:2021:605, paragraphs 45 and 46).

45In the present case, the referring court seeks to determine, in essence, whether a Member State of residence may be considered as released from that obligation by reason of the actual existence of a bilateral tax convention by which that Member State and the Member State of employment apportioned the taxation of the total income of a taxpayer and, in proportion to that apportionment, the taking into account of that taxpayer’s personal and family circumstances, even though that convention is not applied by that second Member State in a way which leads, in practice, to all of those circumstances being duly taken into account in one or other of those two Member States.

46In that regard, it should be borne in mind that the basis of the case-law recalled in paragraph 44 above lies in the obligation for the Member States to exercise their powers of taxation in a non-discriminatory way in respect of EU nationals who have exercised their right to freedom of movement for workers, guaranteed in Article 45(1) and (2) TFEU.

47Where the Member State of residence concludes a bilateral tax convention by which that Member State and the Member State of employment apportion the taxation of the total income of taxpayers who have exercised their right to freedom of movement for workers and, in proportion to that apportionment, the taking into account of their personal and family circumstances, the Member State of residence must be regarded as having exercised its powers in a non-discriminatory manner only if, as a result of the application of the provisions of that convention in each of those Member States, the taxpayers concerned are guaranteed that, as the end result, as in the case of resident taxpayers who do not have income from another Member State, all their personal and family circumstances will be duly taken into account.

48It should be noted that the principle of non-discrimination, as given concrete expression in particular in Article 45(1) and (2) TFEU, is intended to eliminate all measures which, in the field of the freedom of movement for workers, treat a national of another Member State more severely, or place him or her in a situation less advantageous from a legal or a factual point of view, than that of one of the Member State’s own nationals in the same circumstances (see, to that effect, judgment of 13 December 1984, Haug-Adrion, 251/83, EU:C:1984:397, paragraph 14).

49Consequently, where a Member State of residence agrees with other Member States in order to transfer to them part of the obligation to take into account all the personal and family circumstances of taxpayers residing in its territory, the Member State of residence will be regarded as having exercised its powers of taxation in a non-discriminatory manner in respect of EU nationals who have exercised their right to the freedom of movement for workers, only if it follows from that exercise that those nationals are not placed in a less advantageous legal or factual situation compared with resident taxpayers who have not exercised their right to the freedom of movement for workers.

50By contrast, where a Member State of residence concludes with a State of employment such a bilateral tax convention, but it is duly found by the courts of that State of residence that, based on the application of that convention in the State of employment, the loss of part of a deduction applicable to taxpayers resident in the Member State of residence on account of their personal and family circumstances is not offset by the corresponding opportunity of obtaining a similar deduction in the State of employment, in proportion to the income received in that State, the Member State of residence must be regarded as not being released from its obligation to take account in full of the personal and family circumstances of resident taxpayers.

51As a result, in so far as it is indeed the application in the State of employment of the tax convention concluded by that State with the State of residence which places, in that latter Member State, the resident taxpayers concerned in a less advantageous situation compared with resident taxpayers who have not exercised their right to freedom of movement for workers, the legislation of that State of residence, in so far as it does not allow those taxpayers to regain, in those circumstances, a right to have their personal and family circumstances taken into account in full, must be regarded as imposing a restriction on the freedom of movement for workers.

52Such a restriction can be permissible only if it is justified by overriding reasons in the public interest (judgment of 14 March 2019, Jacob and Lennertz, C‑174/18, EU:C:2019:205, paragraph 44 and the case-law cited) or if it relates to situations which are not objectively comparable (see, to that effect, judgment of 17 July 2014, Nordea Bank Danmark, C‑48/13, EU:C:2014:2087, paragraph 23).

53In the present case, however, neither the referring court nor the Belgian Government has referred to overriding reasons in the public interest capable of constituting such a justification, such as the need to ensure the coherence of the Belgian tax system. In addition, the identification of the restriction in paragraph 51 above is based precisely on an analysis of the comparability of the situations of, on the one hand, a resident taxpayer who has exercised his or her right to freedom of movement for workers and in respect of whom the Member State of residence applies a tax convention, such as that described by the referring court, and, on the other, in principle, a resident taxpayer who has not exercised such a right.

54In the light of the above, the answer to the question referred for a preliminary ruling is that Article 45 TFEU must be interpreted as precluding national legislation the application of which leads to the loss in part of the benefit of a tax deduction designed to take account of the personal and family circumstances of resident taxpayers in one Member State, where they receive employment income in a second Member State, which is exempt from tax in the Member State of residence under a bilateral tax convention, whereas resident taxpayers who have no income from another Member State wholly benefit from that deduction, where, under that bilateral tax convention, the loss of that part of that deduction should have been offset, in the second Member State, by the corresponding opportunity to obtain a similar deduction, in proportion to the income received in the second Member State, but that that was not the case based on the application of that convention in the second Member State, provided that there is no overriding reason in the public interest capable of justifying such a loss.

Costs

55Since these proceedings are, for the parties to the main proceedings, a step in the action pending before the referring court, the decision on costs is a matter for that court. Costs incurred in submitting observations to the Court, other than the costs of those parties, are not recoverable.

Operative part

On those grounds, the Court (Fifth Chamber) hereby rules: Article 45 TFEUmust be interpreted as precluding national legislation the application of which leads to the loss in part of the benefit of a tax deduction designed to take account of the personal and family circumstances of resident taxpayers in one Member State, where they receive employment income in a second Member State, which is exempt from tax in the Member State of residence under a bilateral tax convention, whereas resident taxpayers who have no income from another Member State wholly benefit from that deduction, where, under that bilateral tax convention, the loss of that part of that deduction should have been offset, in the second Member State, by the corresponding opportunity to obtain a similar deduction, in proportion to the income received in the second Member State, but that that was not the case based on the application of that convention in the second Member State, provided that there is no overriding reason in the public interest capable of justifying such a loss.