Property gains tax: Federal Supreme Court requires full tax deferral for mixed gifts

Summary of the article

In its ruling 9C_271/2025 of December 22, 2025, the Federal Supreme Court clarified a fundamental issue regarding the deferral of real estate gains tax in the case of mixed gifts, which had previously been handled differently in different cantons. It states that Art. 12 para. 3 lit. a StHG (Tax Harmonization Act) provides for a complete deferral of tax in the case of mixed gifts, rather than a partial deferral. Cantonal practices that limit the tax deferral proportionally to the gratuitous portion are contrary to federal law. Shortly before, the canton of Lucerne had also adapted its practice. These developments are of great importance for succession planning.

Context

Art. 12 para. 3 lit. a StHG stipulates a deferral of real estate gains tax for gifts and advance inheritances. There was some debate as to how this tax deferral should be structured in the case of mixed gifts. A mixed gift exists when there is an obvious imbalance between the benefit and the consideration (objective element) and there is an intention to make a gift (subjective element). While some cantons granted a complete tax deferral for mixed gifts, others limited it to the gratuitous portion and subjected the consideration portion to real estate gains tax. In its ruling 9C_271/2025 of December 22, 2025, the Federal Supreme Court has now provided a definitive answer to the question of deferral of real estate gains tax in the case of mixed gifts.

Presentation of the facts

In 2022, the taxpayers transferred a property to their son at a purchase price of CHF 750,000, with a market value of CHF 1,000,000. The lower courts classified the transfer as a mixed gift due to the significant discrepancy and the established intention to make a gift. Nevertheless, the competent cantonal tax office in St. Gallen granted only a proportional tax deferral and subjected the consideration portion to property gains tax. The taxpayers appealed this decision to the Federal Supreme Court.

Considerations of the Federal Court

The Federal Supreme Court first confirmed that the transfer qualified as a mixed gift. From a legal perspective, it interpreted Art. 12 para. 3 lit. a StHG.

In summary, the Federal Supreme Court concludes that Art. 12 para. 3 lit. a StHG also requires a complete deferral of real estate gains tax in the case of mixed gifts. It bases this conclusion primarily on grammatical, systematic, and historical interpretation; teleological interpretation, on the other hand, proves to be less clear.

The Federal Supreme Court therefore ruled that the partial deferral practice of the canton of St. Gallen was contrary to federal law and obliged the cantons to grant full tax deferral in the case of mixed gifts.

Change in practice in the canton of Lucerne as of September 1, 2025

Even before the Federal Supreme Court ruling on the practice in the canton of St. Gallen, the canton of Lucerne had already changed its practice. This was prompted by a ruling by the Lucerne Cantonal Court on June 25, 2025, which deemed the previous administrative practice to be inadmissible. Since September 1, 2025, mixed gifts have been treated in the same way as advance inheritance payments.

Under the new practice, property gains tax is deferred in full for mixed gifts if there is an obvious discrepancy of at least 25% of the market value between the market value of the property and the consideration paid by the buyer. In other words, the consideration may not exceed 75% of the market value. If this condition is met, the tax deferral applies regardless of whether the transfer actually results in a gain or a loss. To determine the relevant market value, the tax authorities generally use the applicable non-agricultural cadastral valuation as the presumed market value. If the taxpayer claims a higher market value, they bear the burden of proof.

It is also noteworthy that the new practice expressly applies to transfers from parents to children and to their spouses or partners. This eliminates the two-stage process that was sometimes used in the past, whereby a property was first transferred to the child and then transferred proportionally to their partner. In future, the only decisive factor for the complete deferral of real estate gains tax will be that the requirements for a mixed gift are met.

Impact of the Federal Court ruling on tax practice and conclusion

The ruling has significant implications for cantonal property gains tax practice. It obliges the cantons to grant full tax deferral for mixed gifts, provided that the conditions for a mixed gift are met.

As a result, the Federal Supreme Court is strengthening the harmonization of real estate gains tax and preventing economically unjustifiable differentiation within the same transfer process. The decision is consistent, legally sound, and relevant in practice.

However, the ruling shifts the focus to the classification as a mixed gift. According to federal court Jurisprudence , a mixed gift Jurisprudence when the parties deliberately set the price below the true value in order to transfer the difference free of charge. A corresponding intention to make a gift is presumed if there is an obvious disproportion between the performance and the consideration. It is precisely here that cantonal differences continue to exist: in some cases, a discrepancy is assumed if the consideration is more than 20 to 25% below the market value (e.g., the cantons of Zurich, St. Gallen, Schwyz, Aargau, and Basel-Landschaft), while in others, more differentiated approaches apply (including the cantons of Basel-Stadt, Graubünden, Solothurn, Lucerne, Thurgau), while the canton of Bern, for example, does not tolerate any consideration whatsoever.

This means that the legal consequences remain harmonized, but the distinction at the factual level continues to be influenced by cantonal law. Questions of assessment are therefore becoming increasingly important in practice.