If it is only a matter of form, it is generally not required to sign and seal at the same time. Unless the contract clearly stipulates the words "sealed and signed by the legal representative". Therefore, as long as it is a formal company seal, it is generally effective, but it does not rule out that the internal personnel of the company collude with other personnel to stamp the official seal privately. If it is proved to be true, it may be considered invalid. Article 52 of the Contract Law A contract is invalid under any of the following circumstances:

(1) One party enters into a contract by means of fraud or coercion, which harms the interests of the state;

(2) Malicious collusion that harms the interests of the state, the collective or a third party;

(3) Covering up illegal purposes in a legal form;

(4) damaging the public interest;

(5) Violating the mandatory provisions of laws and administrative regulations.

Article 54 The following contracts,

One party has the right to request the people's court or arbitration institution to change or cancel:

(1) Due to a major misunderstanding;

(2) obviously unfair at the time of conclusion of the contract.

If one party leads the other party to conclude a contract against its true meaning by fraud, coercion or taking advantage of others' danger, the injured party has the right to request the people's court or arbitration institution to modify or cancel it.

The people's court or arbitration institution shall not revoke the request of the parties.