Legal subjectivity:

It depends on the specific situation: 1. If it is a supplementary agreement signed between natural persons, generally there is no need to seal it, just sign and confirm it; 2. If it is a company Supplementary agreements signed between parties generally need to be stamped with an official seal, but if the agreement stipulates that the agreement is valid with the signature of the legal representative, then there is no need to stamp it. Article 502 of the Civil Code: A contract established in accordance with the law shall take effect from the time of its establishment, unless otherwise provided by law or otherwise agreed upon by the parties. In accordance with the provisions of laws and administrative regulations, if the contract must undergo approval and other procedures, the provisions shall be followed. If the failure to go through approval and other procedures affects the effectiveness of the contract, it will not affect the effectiveness of the contract's obligation clauses such as submission for approval and related clauses. If the party that should go through the application approval and other procedures fails to perform its obligations, the other party may request that it bear liability for violating such obligations. In accordance with the provisions of laws and administrative regulations, if the modification, transfer, termination, etc. of a contract require approval and other procedures, the provisions of the preceding paragraph shall apply. Legal objectivity:

Civil Code

Article 490

If the parties conclude a contract in the form of a contract, both parties shall sign and seal it. Or a contract is formed when a fingerprint is pressed. Before signing, sealing or fingerprinting, one party has performed its main obligations and the contract is established when the other party accepts it.

Civil Code

Article 510

After the contract takes effect, the parties have not agreed on the quality, price or remuneration, place of performance, etc. or If the agreement is not clear, it can be supplemented by agreement;

If a supplementary agreement cannot be reached, it will be determined according to the relevant terms of the contract or transaction practices.