Provisional text
JUDGMENT OF THE COURT (Sixth Chamber)
12 March 2026 (*)
( Reference for a preliminary ruling – Freedom of movement for workers – Income tax – Tax supplement on the income tax of natural persons which may be established by the municipalities or agglomerations in which those persons reside – Surcharge on income tax borne by non-residents for tax purposes paid to the State – Fiscal burden on non-residents for tax purposes that is heavier than that borne by tax residents of
a Member State – Comparable situations – No justification )
In Case C‑119/24 [Chefquet], (i)
REQUEST for a preliminary ruling under Article 267 TFEU from the Cour d’appel de Liège (Court of Appeal, Liège, Belgium), made by decision of 5 February 2024, received at the Court on 14 February 2024, in the proceedings
DK,
JO
v
État belge,
THE COURT (Sixth Chamber),
composed of I. Ziemele, President of the Chamber, A. Kumin (Rapporteur) and S. Gervasoni, Judges,
Advocate General: N. Emiliou,
Registrar: A. Calot Escobar,
having regard to the written procedure,
after considering the observations submitted on behalf of:
–        DK and JO, by C. Lourtie, avocate,
–         the Belgian Government, by S. Baeyens, P. Cottin and C. Pochet, acting as Agents,
–        the European Commission, by A. Ferrand and W. Roels, acting as Agents,
after hearing the Opinion of the Advocate General at the sitting on 4 September 2025,
gives the following
Judgment
1        This request for a preliminary ruling concerns the interpretation of Article 45 TFEU.
2        The request has been made in proceedings between DK and JO, two natural persons residing for tax purposes in France,
who gain a portion of their employment and property income in Belgium, and the Belgian State, as regards their being made liable
in Belgium over a period of several years
to income tax augmented by a
tax surcharge payable in that Member State by non-resident tax payers (‘the tax surcharge at issue’), as
established by analogy with the supplementary municipal tax for which tax residents of that Member State are liable (‘the supplementary municipal tax at issue’).
Legal context
European Union law
3        Article 45 TFEU reads as follows:
‘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.
3.      It shall entail the right, subject to limitations justified on grounds of public policy, public security or public health:
(a)      to accept offers of employment actually made;
(b)      to move freely within the territory of Member States for this purpose;
(c)      to stay in a Member State for the purpose of employment in accordance with the provisions governing the employment of nationals of that State laid down by law, regulation or administrative action;
(d)      to remain in the territory of a Member State after having been employed in that State, subject to conditions which shall be embodied in regulations to be drawn up by the [European] Commission.
4.      The provisions of this Article shall not apply to employment in the public service.’
Belgian law
4        Article 245 of the Code des impôts sur les revenus (Income Tax Code) of 10 April 1992 (Moniteur belge of 30 July 1992, p. 17120; ‘the CIR 92’), as applicable in respect of the 1992 to 2003 tax years, provided:
‘The tax established in accordance with Articles 243 to 244 [relating to tax on the income of non-residents] shall be increased by a supplement of six percent for the benefit of the State, which shall be calculated in accordance with the rules set out in Article 466. …’
5        By Article 398 of the Loi-programme (Programme Law) of 24 December 2002 (Moniteur belge of 31 December 2002, p. 58686), a new paragraph was added to Article 245 of the CIR 92, applicable from the 2005 tax year, which provides that ‘the King may, by decree deliberated in the Council of Ministers, raise those additional percentages to a maximum of seven percent’. As of that latter tax year, the amount of the additional percentages referred to in the first paragraph of Article 245 of the CIR 92 was set at seven percent.
6        Article 465 of the CIR 92 provides:
‘…
agglomerations and municipalities may establish a supplementary tax on
the taxation of natural persons.’
7        Article 466 of the CIR 92 states:
‘The supplementary municipal tax on the taxation of natural persons and the supplementary agglomeration tax on the taxation of natural persons shall be calculated on the basis of the taxation of natural persons as assessed:
before the deduction of advance payments …, withholding taxes, the fixed percentage of foreign tax and tax credits …;
before the application of increases …, relief … and tax increases …’
8        Article 467 of the CIR 92 provides:
‘The supplementary tax on the taxation of natural persons shall be determined either by the municipality or the agglomeration, and shall be borne by residents of the Kingdom who are liable for tax respectively in that municipality or in the municipalities forming part of that agglomeration.’
9        Article 468 of the CIR 92 states:
‘The supplementary
tax shall be established for all taxpayers in the same agglomeration or municipality at a uniform percentage of the tax payable to the State. If that percentage includes a fraction, it must be limited to one decimal place; that percentage may not exceed 1 [%] where the tax is imposed by an agglomeration. No reductions, exemptions or exceptions may be applied to the supplementary
tax.’
The dispute in the main proceedings and the question referred for a preliminary ruling
10      DK and JO, the applicants in the main proceedings, are natural persons who were resident for tax purposes in France in the tax years of 1992 to 1998, 2001 to 2003 and 2007 to 2009 (‘the tax years at issue’). During those years, DK mainly carried out paid employment as a research director at the National Centre for Scientific Research in Paris (France) and, additionally, he was employed part-time as a lecturer at several universities in Belgium, that latter employment having generated less than 25% of his total income from employment from Belgian and foreign sources. His spouse, JO, was in paid employment in France between 1992 and 1998 but has not been in employment since 2000. In addition, it is apparent from the information available to the Court that, during the tax years at issue, the applicants in the main proceedings owned property in Belgium.
11      In respect of those tax years,
they were taxed as non-residents for tax purposes by the Belgian authorities on their income from employment and property that arose in Belgium. In accordance with Article 245 of the CIR 92, the income tax for which they were liable on that basis was increased by the tax surcharge at issue at a rate of 6%, for the 1992 to 1998 and 2001 to 2003 tax years, and at a rate of 7% for the 2007 to 2009 tax years.
12      The applicants in the main proceedings contested the income tax contributions established in respect of the tax years at issue and lodged a number of complaints in that regard, it being noted that,
in respect of some of those tax years, DK alone lodged an objection. Those complaints were rejected by several administrative decisions as in part inadmissible and in part unfounded, only the complaints relating to the 1993 and 2008 tax years being upheld in part.
13      The applicants in the main proceedings therefore brought actions before the Tribunal de première instance de Namur (Court of First Instance, Namur, Belgium) against those decisions. By judgment of 20 January 2016, that court joined the actions and dismissed them as in part inadmissible and in part unfounded.
14      In addition, by that judgment, the court made a reference to the Cour constitutionnelle (Constitutional Court, Belgium) for a preliminary ruling. By judgment of 6 June 2019, the latter court held, inter alia, that Article 245 of the CIR 92, as applicable in the 1992 to 2009 tax years, did not bring about unjustified discrimination to the detriment of persons who were not resident for tax purposes in Belgium in contravention of Articles 10 and 11 of the Belgian Constitution.
15      On 3 February 2020, the applicants in the main proceedings brought an appeal against the judgment of 20 January 2016 before the Cour d’appel de Liège (Court of Appeal, Liège, Belgium), which is the referring court.
16      It is apparent from the order for reference that the applicants in the main proceedings, inter alia, have raised a question
before the appeal court of the compatibility of Article 245 of the CIR 92 with Article 45 TFEU since it is only persons who are not resident in Belgium for tax purposes who are subject, under Article 245, to a tax surcharge of between 6 and 7% of income tax, which is paid to the State and has been established by analogy with the supplementary municipal tax at issue, as
provided for in Article 466 of the CIR 92 and which is payable by tax residents
of that Member State.
17      The Belgian State, in essence, contends that the referring court should uphold the judgment of 20 January 2016.
18      As regards the compatibility of Article 245 of the CIR 92 with Article 45 TFEU, the referring court takes the view, as does the Cour constitutionnelle (Constitutional Court), that, by subjecting persons not resident for tax purposes in Belgium to the tax surcharge at issue, Article 245 seeks, as indicated by the travaux préparatoires for the law that includes that latter article, to avoid any discrimination between tax residents of that Member State, who are subject to the supplementary municipal tax at issue, and non-residents, and to ensure that the latter contribute, in a proportionate manner, to the financing of tasks in the public interest in so far as they benefit in general terms from the facilities and services provided by the Belgian public authorities.
19      Moreover, the tax surcharge does not cause manifestly disproportionate effects since it is calculated in proportion to the tax due on income generated or received in that Member State. Furthermore, the tax on second residences in that Member State or the residence tax in France, to which non-residents may be subject, do not have the same purpose or the same function as that tax surcharge and are therefore not comparable to it. The tax surcharge in question is calculated in accordance with the same rules as the supplementary municipal tax at issue, but it is collected for the benefit of the State and, therefore,
it has neither the same character nor the same aim as that latter tax.
20      In those circumstances, the Cour d’appel de Liège (Appeal Court, Liège) decided to stay the proceedings and to refer the following question to the Court of Justice for a preliminary ruling:
‘Does Article 45 TFEU preclude the application of Article 245 [of the CIR 92], in so far as that article subjects non-resident taxpayers to a State tax supplement of 6-7%, as compared to that which they would pay if they were residents of the Kingdom [of Belgium], that supplement being imposed by analogy with the local tax imposed by Belgian agglomerations and municipalities on residents of the Kingdom [of Belgium] who have their principal residence in those agglomerations and municipalities?’
Consideration of the question referred
Admissibility
21      Without formally raising an objection of inadmissibility, the applicants in the main proceedings express doubts as to the admissibility of the present request for a preliminary ruling, arguing that the statement of reasons for the request does not satisfy the requirements relating to the content of requests for a preliminary ruling, laid down in Article 94 of the Rules of Procedure of the Court of Justice and in paragraphs 14, 15, 19 and 20 of the Recommendations to national courts and tribunals in relation to the initiation of preliminary ruling proceedings (OJ 2019 C 380, p. 1; ‘the Recommendations’), formulated by the Court of Justice of the European Union, which are now set out in paragraphs 14, 15, 19 and 20 of the Recommendations to national courts and tribunals in relation to the initiation of preliminary ruling proceedings (OJ C C/2024/6008), since the question referred for a preliminary ruling does not appear in a separate part of the order for reference and since that order does not contain a statement of the facts or the relevant national provisions in the present case.
22      In that regard, it should be borne in mind that under settled case-law, the need to provide an interpretation of EU law which will be of use to the referring court requires that court to define the factual and legislative context of the questions it is asking or, at the very least, to explain the factual circumstances on which those questions are based (judgments of 26 January 1993, Telemarsicabruzzo and Others, C‑320/90 to C‑322/90, EU:C:1993:26, paragraph 6, and of 16 October 2025, Braila Winds, C‑391/23, EU:C:2025:799, paragraph 30).
23      The information provided in orders for reference serves not only to enable the Court to give useful answers to the questions referred by the national court, but also to ensure that it is possible for the governments of the Member States and other interested parties to submit observations in accordance with Article 23
of the Statute of the Court of Justice of the European Union. It is the Court’s duty to ensure that that opportunity is safeguarded, given that, under that provision, only the orders for reference are notified to the interested parties (judgment of 16 October 2025, Braila Winds, C‑391/23, EU:C:2025:799, paragraph 31 and the case-law cited).
24      Those cumulative requirements concerning the content of an order for reference are expressly set out in Article 94 of the Rules of Procedure, of which the referring court is supposed, in the context of the cooperation instituted by Article 267 TFEU, to be aware and which it is bound to observe scrupulously. They are also referred to in paragraphs 13, 15 and 16 of the Recommendations (judgment of 16 October 2025, Braila Winds, C‑391/23, EU:C:2025:799, paragraph 32 and the case-law cited).
25      In the present case, it must be stated that the information provided in the order for reference serves not only to enable the Court to give a useful answer to the question referred, but also to ensure that it is possible for the governments of the Member States and other interested parties to submit observations in accordance with Article 23 of the Statute of the Court of Justice of the European Union.
26      First of all, even though the factual context of the dispute in the main proceedings is set out succinctly, it nevertheless includes all the information necessary for those purposes. Further, while it is true that the content of Article 466 of the CIR 92, relating to the calculation of the supplementary municipal tax at issue, is not given in full in the order for reference, it is sufficient to note, first, that Article 245 of the CIR 92, reproduced verbatim in that decision, forms the legal basis for the imposition of the tax surcharge at issue on the applicants in the main proceedings. Second, the exact content of Article 466, which appears in the written observations of the applicants, is secondary since Article 245 refers only to Article 466 as regards the calculation of that supplement and since the order for reference makes clear that the surcharge is calculated in the same way as that tax. Lastly, under paragraph 19 of the Recommendations, the question or questions referred must be set out in a separate and clearly identified part of the order for reference. In the present case, it must be stated that the question referred has been set out at the end of that decision, in a separate paragraph within the operative part.
27      In those circumstances, this request for a preliminary ruling is admissible.
Substance
28      By its question, the referring court asks, in essence, whether Article 45 TFEU must be interpreted as precluding national legislation under which the income tax imposed,
in a Member State, on non-residents for tax purposes is increased by a tax surcharge at a fixed rate for the benefit of that State, which has been established by analogy with a
supplementary tax on the income tax payable by tax residents of that State for the benefit of agglomerations or municipalities which choose to introduce that tax and which determine its rate.
29      As a preliminary point, it must be borne in mind that, according to the case-law of the Court, although direct taxation falls within their competence, Member States must, however, exercise that competence consistently with EU law and particularly the fundamental freedoms guaranteed by the TFEU (judgment of 30 October 2025, Attal et
Associés, C‑321/24, EU:C:2025:836, paragraph 27 and the case-law cited).
The applicable fundamental freedom
30      It is necessary to determine whether Article 45 TFEU is applicable to the dispute in the main proceedings.
31      According to settled case-law, any EU national who, irrespective of his or her place of residence and his or her nationality, has exercised the right to freedom of movement for workers and who has been employed in a Member State other than that of residence falls within the scope of Article 45 TFEU (judgment of 15 July 2021, État belge (Loss of tax advantages in Member State of residence), C‑241/20, EU:C:2021:605, paragraph 20 and the case-law cited).
32      Even though, in the present case, DK and JO’s nationality is not specified in the order for reference, that order is, nevertheless, based on the premiss that they are nationals of a Member State.
33      As is apparent from paragraph 10 above, DK, as a tax resident in France, carried out paid employment in Belgium during the tax years at issue, such that his situation falls within the scope of Article 45 TFEU.
34      On the other hand, according to the information available to the Court, JO only had paid employment during those years in France, where she is resident for tax purposes, and she has not been in paid employment since 2000, with JO’s only Belgian income in the course of those years being the income from property in respect of which the applicants in the main proceedings were taxed by the Belgian authorities, as referred to in paragraphs 10 and 11 above.
35      As regards property investments, in accordance with settled case-law, national measures which govern transactions by which non-residents make such investments on the territory of a Member State may come within the scope of both Article 49 TFEU, relating to freedom of establishment, and Article 63 TFEU, relating to the free movement of capital (judgment of 7 April 2022, Veronsaajien oikeudenvalvontayksikkö (Exemption of contractual investment funds), C‑342/20, EU:C:2022:276, paragraph 39 and the case-law cited).
36      In that regard, it is clear from settled case-law that, in order to determine whether national legislation comes within the scope of one or other of the fundamental freedoms guaranteed by the FEU Treaty, the purpose of the legislation concerned must be taken into consideration and, where it is not clear from the latter under which of the fundamental freedoms that legislation falls predominantly, the facts of the case in point are taken into account (judgment of 7 April 2022, Veronsaajien oikeudenvalvontayksikkö (Exemption of contractual investment funds), C‑342/20, EU:C:2022:276, paragraphs 35 and 36 and the case-law cited).
37      That being said, in order for the provisions relating to freedom of establishment to apply, it is generally necessary to have secured a permanent presence in the host Member State and, where immovable property is purchased and held, that property should be actively managed (judgment of 7 April 2022, Veronsaajien oikeudenvalvontayksikkö (Exemption of contractual investment funds), C‑342/20, EU:C:2022:276, paragraph 42 and the case-law cited).
38      Having regard to the preceding guidance, it will be for the referring court to determine whether JO’s situation falls within the scope of Article 45 TFEU, as the wording of the request for a preliminary ruling suggests, or whether it should rather be assessed in the light of Article 49 or Article 63 TFEU, on the understanding that, in those latter cases, the Court’s answer as based on Article 45 TFEU would be transposable, mutatis mutandis (see, by analogy, judgments of 28 February 2013, Beker, C‑168/11,
EU:C:2013:117, paragraph 45, and of 14 March 2019, Jacob and Lennertz, C‑174/18, EU:C:2019:205, paragraph 23).
Whether there is a restriction on the freedom of movement for workers
39      Article 45(2) TFEU provides that freedom of movement for workers entails 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.
40      It should be observed, in that respect, that the Court has repeatedly held that the principle of equal treatment laid down in Article 45(2) TFEU prohibits not only direct discrimination on the ground of nationality but also all indirect forms of discrimination which, by the application of other criteria of differentiation, such as the criterion of residence, lead in fact to the same result (judgments of 12 February 1974, Sotgiu, 152/73, EU:C:1974:13, paragraph 11, and of 30 May 2024, Finanzamt Köln-Süd (Voluntary assessment requested by a partially taxable person), C‑627/22, EU:C:2024:431, paragraph 83 and the case-law cited).
41      In particular, the principle of equal treatment with regard to remuneration would be rendered ineffective if it could be undermined by discriminatory national provisions on income tax
(judgment of 10 March 2022, Commission v Belgium (Deduction of maintenance payments), C‑60/21, EU:C:2022:172, paragraph 17 and the case-law cited).
42      In the present case, it is apparent from the order for reference that the tax surcharge at issue, which must be paid by those who are non-residents for tax purposes in Belgium, was introduced by Article 245 of the CIR 92 with reference to the supplementary municipal tax at issue, which is paid solely by tax residents of that Member State, in order to ensure that those two categories of taxpayers contribute in proportion to their income sourced in Belgium and, therefore, to impose the same tax burden on them. Consequently, the introduction of that tax surcharge is not, by itself, liable to have a greater effect on workers who are nationals of other Member States.
43      That analysis is not undermined by the arguments of the applicants in the main proceedings by which they assert that they already pay a residence tax in France, that is to say, in their State of residence for tax purposes, which leads to their being double-taxed. It must be held, as the Advocate General observed in point 46 of his Opinion, that the taxation of the rental value of a dwelling has no connection with income generated in a Member State, with the result that that imposition cannot be treated as equivalent to taxation based on that income (see, to that effect, judgment of 21 May 2015, Pazdziej, C‑349/14, EU:C:2015:338, paragraphs 21 to 23). Accordingly, it cannot,
on any view, be considered that the applicants in the main proceedings have been subject to double taxation owing to the fact they have been required to pay both the residence tax in France and the tax surcharge at issue in Belgium.
44      However, it is apparent from the documents available to the Court that the tax surcharge at issue, which is applicable, irrespective of nationality, to all those who are non-residents for tax purposes who have income
in Belgium, subjects those individuals, in certain situations, to a heavier tax burden than that imposed on Belgian tax residents in respect of that same income. Indeed, subject to verification by the referring court, in those Belgian municipalities or agglomerations in which the competent local authority has not introduced the supplementary municipal tax at issue or has set its rate at a level below the rate of the tax surcharge, the tax residents of those municipalities or agglomerations
enjoy more favourable tax treatment than non-residents who are liable for the tax surcharge at issue.
45      It is true, as is apparent from the documents before the Court, that
in other Belgian municipalities or agglomerations,
the rate of the supplementary municipal tax at issue is higher than the rate of the tax surcharge at issue. Accordingly, it is only in some Belgian municipalities or agglomerations
that tax residents face a lighter tax burden than non-residents for tax purposes as regards income generated in Belgium.
46      In that regard, it should be borne in mind that in order for a measure to be treated as being indirectly discriminatory, it is not necessary for it to have the effect of placing at an advantage all the nationals of the State in question or of placing at a disadvantage only nationals of other Member States but not nationals of the State in question (judgment of 15 June 2023, Ministero dell’Istruzione, dell’Università e della Ricerca (Special lists), C‑132/22, EU:C:2023:489, paragraph 30 and the case-law cited). Even a Member State’s tax system that is favourable to non-resident tax payers more often than not may constitute indirect discrimination against the latter where, in certain cases, it proves to be disadvantageous to them (see, to that effect, judgment of 2 June 2016, Pensioenfonds Metaal en Techniek, C‑252/14, EU:C:2016:402, paragraph 38).
47      The difference in treatment noted in paragraph 44 above is liable to act mainly to the detriment of nationals of other Member States, since non-residents are most frequently non-nationals (see, to that effect, judgments of 27 June 1996, Asscher, C‑107/94, EU:C:1996:251, paragraph 38, and of 16 May 2024, Hocinx, C‑27/23, EU:C:2024:404, paragraph 35), with the result that it constitutes a restriction on the freedom of movement for workers which, as a rule, is prohibited
by Article 45 TFEU.
48      Such a restriction is permissible only if it relates to situations which are not objectively comparable or if it is justified by an overriding reason in the public interest (judgment of 22 June 2017, Bechtel, C‑20/16, EU:C:2017:488, paragraph 52 and the case-law cited).
49      In that regard, in relation to direct taxes, residents and non-residents are generally not in comparable situations, since income received in the territory of a Member State by a non-resident is in most cases only a part of his or her total income, which is concentrated at his or her place of residence, and a non-resident’s personal ability to pay tax, determined by reference to his or her aggregate income and his or her personal and family circumstances, is easier to assess at the place where his or her personal and financial interests are centred, which is generally the place of his or her usual abode (judgments of 14 February 1995, Schumacker, C‑279/93, EU:C:1995:31, paragraphs 31 and 32, and of 10 March 2022, Commission v Belgium (Deduction of maintenance payments), C‑60/21, EU:C:2022:172, paragraph 19 and the case-law cited).
50      Accordingly, there can be a restriction on the freedom of movement for workers, for the purposes of Article 45 TFEU, only if, notwithstanding their residence in different Member States, it is established that, having regard to the aim as well as the purpose and content of the national provisions at issue, resident and non-resident taxpayers are in a comparable situation (see judgments of 10 March 2022, Commission v Belgium (Deduction of maintenance payments), C‑60/21, EU:C:2022:172, paragraph 21, and of 27 February 2025, Dyrektor Krajowej Informacji Skarbowej (Management form of a UCI), C‑18/23, EU:C:2025:119, paragraph 78 and the case-law cited).
51      Only the relevant distinguishing criteria laid down by the legislation in question must be taken into account in determining whether the difference in treatment resulting from that legislation reflects an objective difference in situations (judgment of 27 February 2025, Dyrektor Krajowej Informacji Skarbowej (Management form of a UCI), C‑18/23, EU:C:2025:119, paragraph 79 and the case-law cited).
52      In the present case, as is apparent from paragraph 42 above, the tax surcharge at issue was introduced in order to ensure that non-residents for tax purposes are subject to the same tax burden as that imposed on Belgian tax residents on the basis of the supplementary municipal tax at issue. As the Belgian Government stated in its written observations, that is confirmed both by the Belgian legislature, in the travaux préparatoires for the law including Article 245 of the CIR 92, and by the Belgian Constitutional Court, which considered that the aim pursued by that tax surcharge was to treat non-residents and residents in the same manner in order to avoid the latter being subject to unfavourable treatment that is of detriment to them.
53      As regards the purpose and content of the national legislation at issue in the main proceedings, it should be noted, as the Advocate General observed in point 35 of his Opinion, that although the tax surcharge at issue and the supplementary municipal tax at issue have a different legal basis, the fact remains that those two taxes give rise to an increase in the tax burden on taxable income in Belgium and thus involve taxpayers, whether or not they are tax residents of that Member State, in the financing of public services.
54      Having regard to the aim as well as the purpose and content of the legislation at issue in the main proceedings, it must be held that, with regard to taxes which involve taxpayers in financing the public services of the Member State in which they receive income, and the amount of which is not determined by reference to their personal or family circumstances, in terms of the case-law set out in paragraph 49 above, but is calculated in proportion to the income received in that Member State, residents and non-residents are in a comparable situation.
55      Furthermore, it must be stated that, according to the information provided by the referring court, the basis of assessment of the tax surcharge at issue is determined by reference to that of the supplementary municipal tax at issue, laid down in Article 466 of the CIR 92.
56      In doing so, the legislation at issue in the main proceedings treats non-resident taxpayers in the same way as resident taxpayers and thus accepts the comparable nature of their situations for the purposes of the taxes in question.
57      Although it is true that the tax surcharge at issue is paid to the State, while the supplementary municipal tax at issue is directed to the Belgian municipalities or agglomerations which have put it in place, that difference does not affect the comparability of the situations at issue. Indeed, the imposition of that tax surcharge on non-resident taxpayers is linked
to the fact that they are not ‘taxable residents’
of a particular municipality or agglomeration in that Member State, for the purposes of Article 467 of the CIR 92, and cannot therefore be directly associated with one of those authorities such that they may be made subject, as are resident taxpayers, to that municipal tax.
58      The difference in the level at which the tax surcharge at issue and the supplementary municipal tax at issue are collected is therefore based on a criterion of distinction that is directly and solely due to the place of residence of the tax payers concerned (see, by analogy, judgments of 17 March 2022, AllianzGI-Fonds AEVN, C‑545/19, EU:C:2022:193, paragraph 73, and of 27 April 2023, L Fund, C‑537/20, EU:C:2023:339, paragraph 57),
for the purposes of the case-law referred to in paragraph 40 above, even though non-residents for tax purposes,
who are liable for the tax surcharge at issue, are in a comparable situation to that of Belgian tax residents, who are liable for the supplementary municipal tax at issue.
59      Consequently, in view of the difference in treatment found in paragraph 44 above to the detriment of non-residents for tax purposes, in that they are subject to a heavier tax burden than
certain tax residents of Belgium, something which, however, the referring court must verify, the national legislation at issue in the main proceedings brings about a restriction on the freedom of movements of workers (see, by analogy, judgments of 28 February 2013, Petersen, C‑544/11, EU:C:2013:124, paragraph 46, and of 30 October 2025, Attal et
Associés, C‑321/24, EU:C:2025:836, paragraph 38).
Whether the restriction on the freedom of movement for workers is justified
60      According to settled case-law, in order to be justified, a restriction on the freedom of movement of workers must be appropriate for securing the attainment of a legitimate objective and must not go beyond what is necessary to attain that objective (see, to that effect, judgment of 10 July 2025, Städteregion Aachen, C‑257/24, EU:C:2025:567, paragraph 46 and the case-law cited).
61      In the present case, it should be observed that the referring court and the Belgian Government state that the tax surcharge at issue is intended to prevent discrimination of tax residents of Belgium in relation to non-residents for tax purposes by treating them in the same way, namely by making the latter contribute, in a similar manner to residents, to the financing of public services in proportion to their Belgian-sourced income.
62      In that regard, it should be found, first, that the objective of ensuring that those who are non-resident for tax purposes contribute to the financing of the public services of a Member State in proportion to the income generated in that Member State may indeed constitute a legitimate objective. However, it must be pointed out, as is apparent from paragraph 44 above, that the national legislation at issue in the main proceedings does not impose an equal
tax burden, but
one that
is heavier, in certain situations, for those non-residents in comparison with that of certain residents. Accordingly, the legislation in question is not appropriate for ensuring the attainment of that objective and goes beyond what is necessary in order to attain it.
63      Second, it must be stated that a restriction on the freedom of movement for workers to the detriment of non-resident taxpayers cannot be justified by the objective of preventing reverse discrimination against resident taxpayers (see, by analogy, judgment of 27 June 1996, Asscher, C‑107/94, EU:C:1996:251, paragraphs 51 to 54).
64      Indeed, in accordance with Article 45(2) TFEU, freedom of movement for workers entails the abolition of any discrimination based on nationality between workers of the Member States. As is apparent, in essence, from paragraph 47 above, non-residents are in most cases non-nationals, whereas residents are in most cases nationals.
65      To allow a Member State to justify a restriction on the freedom of movement for workers to the detriment of non-resident taxpayers under Article 45(2) TFEU, on the ground that it is intended to prevent unfavourable treatment of resident taxpayers, would therefore amount to rendering the freedom of movement for workers meaningless. In such a situation, priority would be given to the pursuit of an aim that conflicts with the objective of abolishing all discrimination on grounds of nationality since, by such means, a Member State’s protection of its own nationals would prevail over that of the nationals of other Member States.
66      In addition, it should be borne in mind that a difference in treatment brought about by a Member State to the detriment of its own nationals, which, as relevant, comes within the concept of reverse discrimination, is not taken into consideration by EU law (see, to that effect, judgment of 2 April 2020, PF and Others, C‑830/18, EU:C:2020:275, paragraph 35).
67      In any event, it is appropriate to state that any difference in treatment to the detriment of tax residents in Belgium would not arise in the present case from EU law, but from Belgian law, since the levying of the supplementary municipal tax at issue is by no means required by EU law (see, to that effect and by analogy, judgment of 21 March 2019, Commission v Poland, C‑127/17, EU:C:2019:236, paragraph 62).
68      Consequently, subject to verification by the referring court, the indirect discrimination, under Article 45(2) TFEU, which, in certain situations, is borne by persons who are not resident for tax purposes in Belgium does not appear to be justified.
69      In the light of all the foregoing considerations, the answer to the question referred is that Article 45(2) TFEU must be interpreted as precluding national legislation under which the income tax to which non-residents for tax purposes are subject in a Member State is increased by a flat-rate tax surcharge in favour of that State, established by analogy with a supplementary tax on the income tax payable by tax residents of that State in favour of agglomerations or municipalities which choose to introduce it and which determine its rate, where the resulting tax burden for the non-residents in question is, at least in certain cases, heavier than that to which residents are subject under that tax.
Costs
70      Since these proceedings are, for the parties to the main proceedings, a step in the action pending before the national 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.
On those grounds, the Court (Sixth Chamber) hereby rules:
Article 45(2) TFEU
must be interpreted as precluding national legislation under which the income tax to which non-residents for tax purposes are subject in a Member State is increased by a flat-rate tax surcharge in favour of that State, established by analogy with a supplementary tax on the income tax payable by tax residents of that State in favour of agglomerations or municipalities which choose to introduce it and which determine its rate, where the resulting tax burden for the non-residents in question is, at least in certain cases, heavier than that to which residents are subject under that tax.
[Signatures]
*      Language of the case: French.
i      The name of the present case is a fictitious name. It does not correspond to the real name of any party to the proceedings.