Judgment of the Court (Sixth Chamber) of 12 March 2026.#DK and JO v État belge.#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