Legal analysis: Only the official seal without the legal person’s signature is valid. If 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.

Legal basis: "Payment and Settlement Measures" Article 163 The signature of the unit on the settlement voucher shall be the special financial seal or official seal of the unit plus its legal representative or its authorized representative. The signature or seal of the agent.