Federal Supreme Court, 04.05.2026, 2C_506/2024
Facts
The Spanish tax authorities, suspecting that a taxpayer (the appellant) had their tax residence in Spain rather than Switzerland for the years 2018 to 2020, submitted requests for administrative assistance to the Federal Tax Administration (FTA). These suspicions were based on various indicators such as credit card usage, flights from Barcelona, and the purchase of insurance and payment of expenses in Spain. The request sought to obtain information held by banks, a credit card company, an airline, and the tax administration of the Canton of Thurgau. (consid. A.a)
The Spanish authority specifically requested that the Thurgau tax administration provide copies of applications for tax residence certificates, the legal basis for their issuance, and the appellant's tax returns for the period in question. (consid. A.b) In response, the Thurgau tax administration transmitted to the FTA, among other things, the issued tax residence certificates and the correspondence exchanged on this subject with the lawyers mandated by the appellant. (consid. A.c)
The FTA decided to grant assistance and transmit all the information obtained. The appellant appealed to the Federal Administrative Court (FAC), challenging the transmission of the correspondence with their lawyers on the grounds that it was not foreseeably relevant and was protected by attorney-client privilege. The FAC rejected the appeal, deeming the information relevant and concluding that attorney-client privilege did not apply because the documents had been produced by an authority rather than by the lawyer themselves. The appellant then appealed to the Federal Supreme Court. (consid. B.a, B.b, C)
Law
The Federal Supreme Court notes that administrative assistance between Switzerland and Spain is governed byArticle 25bis of the Double Taxation Convention (DTC CH-ES) and, domestically, by the Tax Administrative Assistance Act (TAAA). The TAAA serves as the implementing legislation for international conventions. (consid. 3.1, 3.2)
The primary condition for assistance is the "foreseeable relevance" of the requested information (Art. 25bis para. 1 DTC CH-ES). This condition is met if there is a reasonable possibility that the information will prove useful for the foreign tax investigation. The requested state only verifies whether the documents have a connection to the stated facts and are likely to be used in the foreign proceedings. A request aimed at establishing a person's tax residence is a legitimate purpose. The prohibition on "fishing expeditions" (Art. 7 let. a TAAA) forbids requests that lack a sufficiently concrete link to the investigation. (consid. 5.1, 5.2)
The second legal issue concerns the limits on the exchange of information, particularly attorney-client privilege. Art. 25bis para. 3 let. c DTC CH-ES (modeled onArt. 26 para. 3 let. c OECD Model Convention) allows a state to refuse to provide information that would reveal professional secrets. According to the OECD Commentary, this protection covers confidential communications between a lawyer and their client within the scope of typical legal practice. (consid. 6.2, 6.3)
Swiss domestic law reflects this approach.Art. 8 para. 6 TAAA, which allows a lawyer to refuse to produce documents, applies only to documents in their possession or that of their assistants. TheArt. 13 para. 1bis APA, while protecting "communications between a party and their lawyer" regardless of where they are stored, does not cover correspondence exchanged between a lawyer and an authority. Furthermore, established case law holds that if a lawyer voluntarily discloses confidential information to a third party (such as an authority), the protection of attorney-client privilege is waived for that information, which will then only be protected by the confidentiality obligations applicable to the recipient (e.g., official secrecy). (consid. 6.5)
Application to the case at hand
The Federal Supreme Court first examines the foreseeable relevance of the documents in dispute. It notes that the Spanish request aims to verify the appellant's tax residence. The tax residence certificates and the related correspondence exchanged between the appellant's lawyers and the Thurgau tax authorities have a concrete and direct link to this objective. These documents are therefore capable of contributing to the investigation and satisfy the condition of foreseeable relevance, dismissing any claims of a "fishing expedition." (consid. 5.3)
The Federal Supreme Court then addresses the appellant's main argument regarding attorney-client privilege. It analyzes the scope of the protection offered by the CH-ES DTA. Referring to the OECD Commentary, it emphasizes that the exception for professional secrecy only covers communications between a lawyer and their client. In this case, the disputed correspondence was exchanged between the appellant's lawyers and a third-party authority (the Thurgau tax administration) and is in the latter's possession. Consequently, it does not fall within the scope of protection of Art. 25bis para. 3 let. c of the CH-ES DTA. (consid. 6.4)
The Court confirms that domestic law leads to the same conclusion. Neither Art. 8 para. 6 TAA (as the documents are not in the lawyer's possession) nor Art. 13 para. 1bis APA (as it concerns correspondence with an authority) can be used to oppose the transmission. By voluntarily communicating this information to the tax administration, the lawyers waived the professional secrecy protection that might otherwise have applied. The transmission of these documents is therefore not contrary to the law. (consid. 6.5, 6.6)
Outcome
The Federal Supreme Court dismisses the appeal. It upholds the Federal Administrative Court's decision authorizing the transmission to Spain of all information, including the correspondence between the appellant's lawyers and the Thurgau tax administration. The legal costs are to be borne by the appellant. (consid. 7)
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