The supplementary agreement is only signed by one party and is generally invalid. If one party fulfills its main obligations and the other party accepts them, the supplementary agreement is established and takes effect, unless it is otherwise stipulated by law or agreed by the parties.

According to the first paragraph of Article 490 of the General Principles of the Civil Law, if the parties conclude a contract in the form of a contract, the contract is established when the parties sign, seal or press their fingerprints. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it.

Article 502 stipulates that a contract established according to law shall take effect upon its establishment, unless otherwise provided by law or agreed by the parties.

Legal objectivity:

civil law

Article 502

A legally established contract shall come into force upon its establishment, except as otherwise provided by law or agreed by the parties.