Swiss Federal Supreme Court, 29.05.2026, 9C_436/2025
Facts
A taxpayer and her spouse, married in 2011, were taxed in the canton of Valais under the expenditure-based taxation regime for the 2012 and 2013 tax periods. The tax returns, signed by a fiduciary, stated a determining income of 200,000 CHF for the couple. Subsequently, the Geneva Cantonal Tax Administration (AFC-GE) initiated tax back-payment and tax evasion proceedings against the spouses, who had not filed a tax return in Geneva. (consid. A.a, A.b)
For the years 2012 and 2013, the AFC-GE proceeded with an ex officio assessment, determining significant global taxable income and wealth for the couple. Specifically for cantonal and communal tax (ICC), it attributed a personal income of 200,000 CHF to the taxpayer for each of the two years. Fines for completed tax evasion (2012) and attempted tax evasion (2013) were also notified to her. Following an appeal that resulted only in a reduction of the fines, and a divorce granted in December 2022, the case was brought before the Geneva judicial authorities. (consid. A.c, A.d, A.e)
The Administrative Court of First Instance, and subsequently the Court of Justice of the Republic and Canton of Geneva, largely rejected the taxpayer's appeals, upholding the inclusion of 200,000 CHF in income for her ICC assessment. The taxpayer then filed a public law appeal with the Federal Supreme Court, challenging the determination of her taxable income and the resulting fines. (consid. B.a, B.b, C)
Law
The Federal Supreme Court reiterates that, when seized of a public law appeal, it applies the law ex officio but only examines the violation of fundamental rights (such as arbitrariness, Art. 9 Cst.) if the grievance is specifically invoked and substantiated. Its power to review harmonized cantonal law is in principle unrestricted, unless federal law leaves room for maneuver to the cantons, in which case the review is limited to arbitrariness. (consid. 2.1, 2.2)
The contested judgment correctly set out the applicable legal principles, in particular: the determination of taxable income (Art. 16 LIFD ; Art. 7 LHID ; Art. 17 LIPP/GE), the joint taxation of spouses living in a common household (Art. 9 para. 1 DBIG ; Art. 3 para. 3 STHG), the termination of joint tax liability between spouses following separation or divorce, and the allocation of tax debt (Art. 13 DBIG ; Art. 12 LIPP/GE), the inquisitorial principle and the burden of proof in tax matters, as well as the conditions for tax evasion. (consid. 4)
Application to the specific case
The cantonal Court of Justice had held that, in the absence of joint tax liability between the ex-spouses (following the divorce), it was justified to take into account the financial transfers from the ex-husband to the appellant. As the latter failed to quantify the amounts received, the lower court did not deem it arbitrary to base its decision on the amount of CHF 200,000 declared to the Valais authorities in the context of expenditure-based taxation. (consid. 5)
The Federal Supreme Court deems this reasoning arbitrary and manifestly unsustainable. Firstly, it is contradictory to acknowledge that the sums paid by the ex-spouse constitute amounts at free disposal within the meaning ofArt. 164 CC (and are therefore fiscally neutral within the context of a common household) and to transform them into taxable income solely on the grounds that joint tax liability has ceased. The end of cohabitation does not alter the nature of these payments; it only justifies an allocation of a validly established tax debt, not the creation of a new taxable base. (consid. 7.1)
Secondly, the Federal Supreme Court deems it inadmissible to transpose an amount of CHF 200,000, set on a lump-sum basis according to lifestyle in the context of expenditure-based taxation (Art. 14 DBIG), to an ordinary tax assessment procedure which must be based on actual income (Art. 16 DBIG). These two tax regimes are based on distinct logics and conditions of application. It is also inconsistent to use the appellant's Valais declarations against her while ignoring her ex-husband's ordinary tax assessment decisions for the same periods, which showed negligible income. (consid. 7.1)
Finally, the Federal Supreme Court held that the appellant could not be required to prove a negative fact (the absence of income), given that she had provided her bank statements and the tax authority had failed to demonstrate the existence of any taxable income. The failure to quantify the amounts received from her ex-spouse did not justify applying a flat-rate amount without a legal basis. The decision of the lower court is therefore arbitrary in its outcome. (consid. 7.1, 7.2)
Outcome
The Federal Supreme Court upheld the appeal regarding cantonal and municipal tax. It set aside the judgment of the Court of Justice dated June 10, 2025. The case is remanded to the Geneva Cantonal Tax Administration for further investigation and the issuance of a new tax assessment for the 2012 and 2013 periods, based on the appellant's actual income rather than the flat-rate amount derived from expenditure-based taxation. The court costs are to be borne by the Canton of Geneva, which must also pay legal fees to the appellant. (consid. 1, 2, 3, 4 of the operative part)