When the specific contents of the contract are not clear, one party shall sign it first, and then supplement the contents of the contract to the signed contract; Then the content of the contract added at this time may be agreed by both parties in advance, or it may be a separate expression of will by one party, which is possible. If the content of the contract supplemented afterwards is completely agreed by both parties through consultation and is the expression of their true meaning, then even if one party signs the blank contract first, we can't deny the validity of the contract just because of this form. Of course, this rarely happens in reality. Generally speaking, if one party signs a blank contract first, most of the contents added afterwards are different from its true meaning, and the reason why one party signs a blank contract is probably fraud, so in this case, the contract can be cancelled, and the contract will be invalid from the beginning after cancellation. Of course, this is a theoretical analysis, but in practice, if you encounter such a situation, if you want to claim that the contract is invalid, you need to prove that when you signed the contract, it was a blank contract, and the contents of the contract were not stated, and now the contents of the contract are not what you really mean. In practice, some parties sign and seal incomplete blank contracts and give them to others directly for the convenience of transaction, which actually hides huge legal risks. If one party of the contract gives the contract with blank contents to the other party, it shall be regarded as unlimited authorization for the contents of the contract, and the other party of the contract may fill in the corresponding contents in the blank part. This contract is protected by law, and it is deemed that both parties have reached an agreement in black and white. After signing a blank contract, once the other party fills in the conditions inconsistent with the previous negotiation, it is difficult to find it invalid in the later stage. If you must sign a blank contract, remember to record the contents of the agreement discussed by recording. Or, write the agreed content on paper and let the person in charge sign it. Wait until there is a formal agreement.

People's Republic of China (PRC) Civil Code

Article 148

If a party commits a civil legal act that goes against its true meaning by fraudulent means, the injured party has the right to request the people's court or an arbitration institution to cancel it. Article 149 of the Civil Code stipulates that if a third party commits fraud, causing one party to commit a civil legal act against its true meaning, and the other party knows or should know about the fraud, the defrauded party has the right to request the people's court or an arbitration institution to cancel it.