Legal basis: Article 490 of the Civil Code of People's Republic of China (PRC). If the parties enter into a contract in the form of a contract, the contract shall be 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. A contract shall be concluded in writing in accordance with the provisions of laws and administrative regulations or the agreement of the parties. If the parties have not concluded a contract in writing, but one party has fulfilled its main obligations and the other party has accepted it, the contract is established.