Valid. Under normal circumstances, a contract with only a signature and no seal should be deemed valid. Stamping is just a formality. The other party's approval or actual performance or the signature of the legal representative all indicate that the contract is valid. Article 490 of the 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 the contract. 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.