Judgment of the Court (First Chamber) of 30 May 2024.#AB v Finanzamt Köln-Süd.#Request for a preliminary ruling from the Finanzgericht Köln.#Reference for a preliminary ruling – Agreement between the European Union and the Swiss Confederation on the free movement of persons – Worker from a Member State who has transferred his residence to Switzerland – Tax concessions – Income tax – ‘Voluntary assessment’ mechanism – Taxpayers who may benefit therefrom – Restriction to partially taxable employed persons resident in a Member State or in a State party to the Agreement on the European Economic Area (EEA) – Equal treatment.#Case C-627/22.