Principle of freedom of form
According to Art. 11 CO, contracts only require a special form for their validity if the law prescribes such a form. In other words, the principle of freedom of form applies in Swiss contract law. And effectively, all contracts that are important for international business can be concluded informally, in particular the purchase contract, service contract, contract for work, licence agreement and distribution agreement. But beware! If the law requires a form and the form is not observed, the contract is void under Swiss law. Most legal systems follow the same principle, but each has its own list of contracts that require written form or a notarial deed; check the list for your country before you rely on an informal agreement.
Forms provided by law
The forms provided by law are simple written form, qualified written form and public notarisation (in the official English translation of the CO: «public deed»). Simple written form means that a contract is printed on paper and signed by hand (Art. 13 f. CO). The latter is also possible by means of a qualified electronic signature (see Chapter 03.04 Qualified electronic signature), e.g. also in PDF format (Art. 14 CO). In the case of qualified written form, for example, individual elements of the contract must be completed by hand, as is the case with a guarantee of up to CHF 2,000; above that amount, a guarantee by a private person even requires public notarisation (Art. 493 CO). Finally, a contract where the law provides for the form of public notarisation must be concluded before a notary public, which is the case, for example, with the purchase of land (Art. 216 CO).
Written form recommended, even where not required
Although the law only rarely requires the written form for contracts, in practice the written form is preferable to oral agreements or agreements by implied conduct*, even if such a document is not even signed but only exchanged by e-mail. In the latter case, the e-mail correspondence containing the agreement should always be kept. Of course, digital written agreements can also be signed digitally (see Chapter 03.04 Qualified electronic signature). Written form facilitates proof, prevents misunderstandings and thus prevents legal or even judicial disputes.
Contractual reservation of the written form
In written contracts, the parties often reserve the right that any changes to the contract must also be made in writing (reservation of the written form). This contributes, among other things, to an orderly and documented further development of the contractual relationship.
*The so-called «implied conduct» (German: «konkludentes Verhalten») means that a contract is concluded by the behaviour of the parties, without an express declaration; see the kiosk example in Chapter 03.01.
Exercise: which form?
Five everyday contracts: (1) buying a used car from a private seller; (2) renting a flat; (3) standing surety for a friend’s loan; (4) buying a plot of land; (5) licensing software by e-mail. Take a guess first: which form does Swiss law require for each? Then ask a chatbot of your choice (Claude, ChatGPT & Co.), first under Swiss law, then under the law of your country, and note where the two differ from your guess and from each other.
In class: we compare the results. Who had all five right?