Generally speaking, it is valid to affix a personal seal to a contract, but if it is a contract signed with a company, it is an official seal, and affixing a personal seal is invalid. According to Article 490 of the General Principles of Civil Law of People's Republic of China (PRC), if the parties conclude a contract in the form of a contract, the contract is established when the parties sign, seal or fingerprint it. 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 A lawfully formed contract shall become effective upon its formation, unless otherwise provided by law or agreed by the parties. Article 493 of the Civil Code of People's Republic of China (PRC), if the parties conclude a contract in the form of a contract, the place where the contract is concluded is the place where the parties finally sign, seal or fingerprint, unless otherwise agreed by the parties.