Federal Supreme Court, 09.17.2026,2C_535/2026
Facts
On September 18 and 24, 2024, the Ukrainian tax authorities submitted several requests for administrative assistance to the Federal Tax Administration (FTA), based on Articles 5 and 18 of the Convention on Mutual Administrative Assistance in Tax Matters (MAC). They requested banking information held by a Swiss institution concerning six Ukrainian companies and one Cypriot company. The FTA granted the assistance via decisions dated March 20 and 24, 2025 (consid 1.2.2).
The companies concerned appealed to the Federal Administrative Court (FAC), challenging in particular compliance with the principles of availability, reciprocity, and subsidiarity. They produced a private expert report casting doubt on the Ukrainian assurances and, alternatively, requested a stay of proceedings. Following the dismissal of their appeals on August 24, 2026, they filed an appeal with the Federal Supreme Court, essentially requesting that the transmission of the disputed banking information be refused (consid 1.2.2 and 1.3).
Law
Pursuant to Art. 83 let. hand84a LTF, an appeal in public law matters in the field of international administrative assistance in tax matters is only admissible if it raises a legal question of principle or concerns a particularly important case within the meaning of Art. 84 para. 2 of the Federal Supreme Court Act (LTF). A legal question of principle implies, in particular, an issue requiring clarification by case law, which is likely to guide practice or affect numerous similar cases. It is the responsibility of the appellant to demonstrate this condition of admissibility (consid 1.1).
The principle of good faith between states, enshrined inArt. 26 of the Vienna Convention on the Law of Treaties, forms the basis of the principle of trust applicable to administrative assistance in tax matters. The requested state must, in principle, rely on the declarations of the requesting state, particularly regarding the foreseeable relevance of the information requested. However, this presumption is not irrebuttable: it can be overturned by concrete and established evidence. In the presence of serious doubts, the requested state may demand further clarification (consid 1.2.1).
A legal question, even one that is potentially fundamental, does not justify the court’s consideration if its resolution would have no impact on the outcome of the dispute. The appeal therefore requires a concrete interest in the requested clarification, excluding any purely abstract examination (consid 1.3).
Application to the specific case
The appellants asked how to overturn the presumption of good faith attached to the declarations of the Ukrainian authority. The Federal Supreme Court considers this question already resolved by its established case law: only concrete and demonstrated elements allow for the questioning of the requesting state's assurances. Determining what constitutes sufficient evidence is a matter of assessing the specific circumstances rather than a new legal question of principle (consid 1.2.3).
The Ukrainian authority had expressly confirmed that it could obtain, in accordance with its domestic law, comparable information and communicate it to Switzerland. The private expert report produced revealed no manifest error, omission, or contradiction capable of undermining these assurances. The FAC was therefore entitled to consider the principles of availability and reciprocity as having been respected (consid 1.2.2).
The appellants also asked whether these principles constituted legally binding obligations that could be invoked in court. However, as their compliance had been established, this question could not alter the outcome of the dispute. The Federal Supreme Court therefore refuses to rule on their legal scope in the abstract, due to the lack of a concrete interest and a decisive legal question of principle (consid 1.3).
Outcome
The Federal Supreme Court declares the appeal inadmissible, as no legal question of principle justifies its examination. The authorized administrative assistance therefore remains unchanged. The court costs of CHF 5,000 are divided equally between the appellants, who are jointly and severally liable. No legal costs are awarded (consid 1.4 and 2).