Depending on the situation:
1. If one party to the contract signs and the other party does not sign in person, but signs it afterwards and the other party accepts it, the contract is also established.
2 If the parties conclude a contract in the form of a contract, the contract is established when both parties sign, seal or fingerprint.
3. Before signing, sealing or fingerprinting, one party has performed its main obligations and the contract is established when the other party accepts it.
4. If the contract is in writing and has only the signature of one party but not the signature or seal of the other party, the contract is invalid.
5. If the contract is in electronic form, a confirmation letter must be signed in advance. Without a confirmation letter, the contract will be invalid.
The law does not prohibit both parties from signing separate contracts. One party signs first, and the other party signs and seals it. As long as both parties agree that the signature and seal are authentic, the contract is established.
Since it is a contract, both parties need to negotiate and then sign for confirmation.
As for whether the contract is effective, it depends on the specific content of the contract. If the contract is the true expression of the intentions of both parties and does not violate legal provisions, and both parties have the qualifications or ability to sign the contract, such a contract is valid.
Legal basis:
"People's Republic of China and Civil Code"
Article 490
The parties adopt a contract If a contract is concluded in writing, the contract is established when both parties sign, seal or fingerprint it. 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 or the parties agree that a contract should be concluded in writing. If the parties do not use writing but one party has performed its main obligations and the other party accepts it, the contract is established.