Legal analysis: If the contract is written and only signed by Party B, but not signed and sealed by Party A, the contract is invalid. If the contract is electronic, a confirmation letter must be signed in advance, otherwise the contract will be invalid. Since it is a contract, it needs to be signed by both parties.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 490 Where the parties conclude a contract in the form of a contract, the contract is formed when the parties sign, seal or fingerprint it. 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.

Article 491 Where the parties conclude a contract by means of letters or data messages, they are letters, data message form contracts and network contracts. It is also required to sign a confirmation letter, and the contract is established when the confirmation letter is signed.