Swiss Federal Supreme Court Clarifies
Requirements for Arbitration Agreements
Concluded via WhatsApp

In its decision of 14 September 2026 (4A_237/2026), the Swiss Federal Supreme Court confirmed that arbitration agreements can in principle be concluded through an exchange of WhatsApp messages. However, the Court held that in the instant case, an arbitration clause contained in general terms and conditions attached to an invoice sent via WhatsApp had not been validly agreed upon by the parties.

Background

The dispute arose from the sale of artworks between a Swiss art dealer and a private collector. In August 2024, the parties negotiated the purchase of an artwork by Miriam Cahn and a collection of five works by other Swiss artists through WhatsApp.

Following the parties' exchanges, the art dealer sent the buyer invoices as four-page PDF attachments via WhatsApp. The invoices contained a reference to arbitration in the small print under "Key Terms" and were accompanied by general terms and conditions providing for arbitration under the Swiss Rules of International Arbitration, with the seat of arbitration in Lucerne.

In subsequent WhatsApp exchanges, the buyer indicated his willingness to pay and responded to certain messages with expressions such as "OK 🙏" and "Bill please". However, the transactions ultimately gave rise to a dispute and the art dealer initiated arbitration proceedings. The sole arbitrator found that the buyer had validly agreed to arbitration by accepting the invoices and the accompanying terms and conditions and issued an award ordering the buyer to pay damages of CHF 402'500 plus interest.

The buyer challenged the award before the Swiss Federal Supreme Court, arguing that no valid arbitration agreement had been concluded.

The Court's reasoning

The Swiss Federal Supreme Court upheld the appeal, set aside the arbitral award, and declared that the sole arbitrator lacked jurisdiction. In reaching its conclusion, the Court clarified several aspects of the conclusion of arbitration agreements through electronic communications:

• WhatsApp could in principle satisfy the formal requirements for arbitration agreements. Under Art. 358 of the Swiss Civil Procedure Code (CPC), an arbitration agreement must be concluded in writing or in another form permitting proof by text. A handwritten or electronic signature is not required. Accordingly, arbitration agreements may validly be concluded by email, SMS or instant messaging services such as WhatsApp or Signal. However, the declarations of intent of both parties must satisfy the text-form requirement.
• Consent to arbitration must be established. The validity of an arbitration agreement requires a sufficiently clear expression of the parties' intention to submit their disputes to arbitration rather than to the state courts. Where no actual agreement of intent can be established, the parties' declarations must be interpreted objectively under the principle of trust. Given the restrictions on judicial remedies resulting from an agreement to arbitrate, such an intention cannot be inferred lightly.
• The informal nature of WhatsApp communications must be taken into account. The Court emphasised that WhatsApp is designed for informal communication and that messages are typically composed and read on mobile phones. Accordingly, it cannot generally be expected that recipients will examine every detail of a multi-page PDF attachment. In the present case, the WhatsApp correspondence did not refer to the general terms and conditions or the arbitration clause. The arbitration provision contained in the invoices' small print was therefore insufficient to establish the buyer's consent.

The Court further observed that an invoice is generally understood as a request for payment rather than an offer to introduce or amend contractual terms. The buyer's subsequent statements concerning payment and his brief WhatsApp responses could not reasonably be interpreted as acceptance of an arbitration clause modifying the contracts already concluded.

In an earlier landmark decision (BGE 142 III 239), the Federal Supreme Court had upheld an arbitration agreement contained in an unsigned draft framework agreement exchanged by email, finding that the parties had reached agreement on the arbitration clause after specifically negotiating its terms. The present decision had a different outcome because the parties' WhatsApp correspondence contained no reference to the arbitration clause or the general terms and conditions, let alone any negotiations concerning them.

Practical implications

The decision confirms that Swiss law accommodates modern forms of electronic communication when concluding arbitration agreements. At the same time, it illustrates the risks of relying on arbitration clauses contained in documents exchanged during the performance of a transaction without clearly establishing the parties' consent.

For businesses negotiating and concluding contracts through WhatsApp or similar messaging services, several precautions are advisable:

• Incorporate arbitration clauses at contract conclusion, not afterwards. Where arbitration is intended, the contractual documentation or communications should clearly refer to the applicable terms and conditions, including the arbitration clause. Merely sending an invoice containing an arbitration clause after the underlying contract has been concluded will not, by itself, establish an agreement to arbitrate.
• Ensure clear and documented acceptance. Where contractual terms are exchanged electronically, an express written acknowledgement of their acceptance reduces the risk of subsequent disputes over the existence of an arbitration agreement. Conversely, a party seeking to avoid being bound to an arbitration agreement from an exchange of drafts should clearly object or insist that the drafts contain a corresponding reservation stating that no arbitration agreement is concluded unless and until the contract is signed.

Ultimately, the judgment serves as a reminder that while electronic communications may simplify the conclusion of contracts and arbitration agreements, parties intending to exclude the jurisdiction of state courts should ensure that their agreement to arbitrate is clearly established and adequately documented.