Legal analysis: In the following situations, the contract signature is invalid and the contract is also invalid:

(1) One party enters into the contract by means of fraud or coercion, harming the country interests;

(2) Malicious collusion to harm the interests of the country, the collective or a third party;

(3) Covering illegal purposes in legal forms;

( 4) Harm the interests of the public;

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

Legal basis: Article 490 of the "People's Republic of China and Civil Code" Where the parties conclude a contract in the form of a contract, the contract is established when both parties sign, seal or fingerprint. Before signing, sealing or fingerprinting, one party has performed its main obligations and the contract is established when the other party accepts it. Laws and administrative regulations stipulate or the parties agree that a contract should be concluded in written form. If the parties do not use written form but one party has performed its main obligations and the other party accepts it, the contract is established.