Key takeaways
WHAT IT IS ABOUT Those who contest a canton's taxing jurisdiction before the Swiss Federal Supreme Court without recognisably also contesting the already final assessment of the other canton risk definitive double taxation. In the case underlying the court decision 9C_652/2025 of June 9, 2026, the Canton of Zurich claimed taxing jurisdiction over a limited liability company (GmbH) with registered seat in the Canton of Zug as of the 2016 tax period because the sole shareholder and managing director resided in the Canton of Zurich and the business activities were carried out abroad (without a fixed place of business). Before the Federal Supreme Court, the company filed within the appeal deadline only a prayer for relief directed against the Canton of Zurich and apparently objected only to the finding that the company's seat was located in Zurich. It submitted the alternative claim for the annulment of the final Zug assessments 2016 to 2019 and the refund of the taxes of CHF 143'922 paid there only after expiry of the 30-day appeal deadline. The Federal Supreme Court did not consider this claim. Sitting as a five-judge panel (decision designated for publication), it expressly abandons the presumption that in tax domicile proceedings an alternative claim against the other canton is implicitly included. In the case at hand, the missing alternative claim could neither be read into the appeal nor be added after expiry of the deadline. The Federal Supreme Court also recalled that there is no legal entitlement to a revision of the final assessment in the other canton.
WHO IS AFFECTED Companies with registered seat in a low-tax canton whose management is effectively exercised elsewhere, as well as their advisers. Also affected are all pending and future intercantonal domicile disputes in which one canton claims taxing jurisdiction retroactively while the canton of the registered seat has already issued final assessments.
NO MORE IMPLIED CONTESTATION
Under a widespread line of previous case law, no strict requirements applied to the contestation of the assessments of the first-assessing canton. The Federal Supreme Court partly considered it sufficient that a party filing a double taxation appeal, as experience shows, does not intend to pay taxes in two cantons. The Federal Supreme Court now expressly abandons this generous line. The general rules on the interpretation of prayers for relief under art. 42 para. 1 of the Federal Act on the Federal Supreme Court (BGG) now apply, without special treatment for double taxation cases. The “Vertrauensprinzip”, under which prayers for relief are interpreted according to the objective meaning a reasonable recipient would attribute to them, remains in place: if the wording of the prayer for relief does not provide conclusive certainty, the presumed intention of the appellant must be determined by reference to the grounds of the appeal. What no longer holds is the natural presumption that an alternative claim against the other canton is implicitly included. If the appeal filed within the deadline lacks clear indications that the assessment decisions of the first-assessing canton are also being contested, such an intention can neither be read into the appeal nor added after expiry of the deadline.
NO LEGAL ENTITLEMENT TO REVISION IN THE OTHER CANTON
Those who omit the alternative claim cannot cure the error afterwards. The Federal Supreme Court holds that no legal entitlement to a revision in the "forgotten" canton can be derived from art. 51 para. 1 lit. a of the Federal Act on the Harmonisation of Direct Taxation at Cantonal and Communal Levels (DTHA) or directly from art. 127 para. 3 of the Federal Constitution. In the present case, the company therefore depends on the goodwill of the Canton of Zug. In its observations, the canton had indicated that it could remedy the double taxation itself through the suspended revision and objection proceedings. There is, however, no legal entitlement to this. Depending on the canton and the procedural history, the procedural omission before the Federal Supreme Court may result in definitive double taxation for the company concerned.
RELEVANCE FOR PRACTICE
The decision highlights the procedural risks in double taxation cases. We recommend formulating the prayers for relief before the Federal Supreme Court expressly "bidirectionally". Specifically, the appeal should contain a principal claim against the canton newly claiming taxing jurisdiction and an alternative claim against the canton that has already issued its assessments, including a claim for refund and interest. This removes any need for an interpretation of the prayers for relief. Those who currently have a double taxation appeal pending before the Federal Supreme Court should immediately review their prayers for relief for bidirectionality and, if necessary, supplement them within the 30-day appeal deadline.
PROCEDURE OVERRIDING THE SUBSTANTIVE CLAIM
The decision is open to criticism in light of the protective purpose of art. 127 para. 3 of the Federal Constitution. According to its own statements, the Federal Supreme Court applies the prohibition of intercantonal double taxation ex officio and with full power of review. At the same time, it lets the principle of party disposition determine the scope of this protection. Those who omit the alternative claim, and whose prayers for relief cannot be interpreted as also contesting the final assessments, lose the constitutional protection for purely formal reasons even though the double taxation is substantively established. At least a claim filed within the deadline with unclear wording remains open to interpretation. This mitigates the strictness but does not eliminate the tension with the constitutional prohibition.
CONCLUSION
With the decision 9C_652/2025, the Federal Supreme Court ends the special procedural treatment of double taxation appeals with regard to the interpretation of prayers for relief. The protection of art. 127 para. 3 of the Federal Constitution applies only to those who invoke it in time and in clearly recognisable form. For advisory practice, the express alternative claim including a request for refund and interest (bidirectional prayers for relief with refund claim) is therefore recommended as the standard in every double taxation appeal.
