TF, 13.10.2026,2C_607/2026
Facts
On October 25, 2024, the competent tax authority of the Republic of Slovenia submitted a request for administrative tax assistance to the Federal Tax Administration (FTA) concerning A.________ and B.________, based on the Convention of January 25, 1988, on Mutual Administrative Assistance in Tax Matters (MAC), in order to verify the legitimacy of their tax residency status in Slovenia (Fact A).
Upon inquiry by the FTA, the requesting authority expressly certified via email on March 24, 2025, that it had exhausted all internal sources of information reasonably accessible under Slovenian law (Fact A).
In a final decision dated October 10, 2025, the FTA granted the requested administrative assistance; this decision was challenged by A.________ and B.________, as well as by affected third parties (C.________ AG, D.________, E.________ AG, and F.________ AG), before the Federal Administrative Court (Fact B).
In a judgment dated September 14, 2026, the Federal Administrative Court dismissed their appeal while ordering the FTA to notify the requesting State of a standard reservation limiting the use of the information to tax proceedings initiated against A.________ and B.________, and reminding them of the confidentiality obligation under Art. 22 of the MAC (Fact B).
A.________ and the other appellants (hereinafter: the appellants) filed an appeal in public law matters with the Federal Supreme Court on September 28, 2026, seeking primarily the annulment of the cantonal judgment and the refusal of assistance, or alternatively, the remand of the case for fact-finding regarding the principle of subsidiarity, as well as a limitation on the transmission of information concerning the third-party companies and the foundation (Fact C).
Law
In matters of international administrative tax assistance, an appeal in public law matters is admissible only if it raises a legal question of principle or involves a particularly important case (Art. 83 let. hand84a LTF) (consid. 1.1).
A legal question of principle implies a novel issue or one of general scope that requires clarification through precedent to guide the practice of lower courts, provided that it is decisive for the concrete outcome of the dispute (consid. 1.1).
Pursuant toArt. 21 para. 2 let. g MAC, the requested State is not required to provide assistance if the requesting State has not exhausted the internal sources of information provided for by its legal system (principle of subsidiarity) (consid. 1.2.1).
However, from the perspective of the principle of good faith (Art. 26 of the Vienna Convention on the Law of Treaties) and the principle of trust governing international treaty relations, the requested State is presumed to rely on the declarations and assurances provided by the foreign authority, a presumption that can only be overturned by objective and proven evidence (consid. 1.2.2).
Furthermore, the condition of foreseeable relevance is met as long as there is a reasonable possibility that the requested information will shed light on the tax situation being examined by the requesting authority, with the Swiss executing authority limited to a simple plausibility check without ruling on the merits of the facts (consid. 1.3.1).
Application to the specific case
The appellants first raise the question of whether the power—rather than the obligation—to refuse assistance in the event of non-compliance with the principle of subsidiarity (Art. 21 para. 2 let. g MAC) exempts the judge from verifying the internal Slovenian procedures when grievances are articulated by the taxpayers (consid. 1.2).
The Federal Supreme Court holds that this issue does not constitute a legal question of principle, as the application of the principle of subsidiarity and the enforceability of the written confirmation provided on March 24, 2025, by the Slovenian State are resolved through the standard application of established case law regarding the principle of trust (consid. 1.2.3).
The question of whether the refusal of assistance based on Art. 21 para. 2 let. g MAC confers discretionary power or an obligation is therefore not decisive in the present case (consid. 1.2.3).
Secondly, the appellants ask whether the accounts and management records of an independent Swiss public-utility foundation are foreseeably relevant for determining the effective tax domicile of the individual founders (consid. 1.3).
The Federal Supreme Court finds that this grievance relates exclusively to the application of the law to the specific case and the verification of factual plausibility as determined by the Federal Administrative Court, without having general jurisprudential significance (consid. 1.3.2 and 1.3.3).
As the admissibility requirements of Art. 84a of the Federal Supreme Court Act are not met, the appeal is inadmissible from the outset, rendering the request for a stay of execution moot (recital 1.4).
Outcome
The Federal Supreme Court declares the public law appeal inadmissible (operative part 1, recital 1.4).
The court costs, set at CHF 5,000, are to be borne jointly and severally by the unsuccessful appellants (operative part 2, recital 2).