It depends: 1. If the construction unit authorizes the project department, the project department will fully perform the contract on behalf of the construction unit, and settlement book confirms that there is no other agreement to the contrary. Then the project department has the right to confirm that the seal of the project department is valid on the settlement book and settlement book of the project; Second, if the construction unit does not authorize the project department, the seal of the project department will be invalid. Article 490 of the Civil Code If the parties conclude a contract in the form of a contract, the contract is established when the parties sign, seal or press their fingerprints. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it. A contract shall be concluded in written form as stipulated by laws, administrative regulations or agreed by the parties. If the parties do not do this in writing, but one party has fulfilled its main obligations and the other party accepts it, the contract is established.