it only needs the signature of the promising party. A letter of commitment is a written expression of the offeree's complete consent to the offer, that is, the offeree agrees to accept all the conditions of the offer and forms a contract with the offeror. Usually, a contract is required to be concluded in writing, and its commitment must also be in writing. The legal effect of acceptance is that once the letter of commitment is made and delivered to the offeror, the contract is established and the offeror may not refuse it. Legal basis: Article 49 of the Civil Code of the People's Republic of China. If the parties conclude a contract in the form of a contract, the contract shall be formed when all 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 writing as stipulated by laws and administrative regulations or agreed by the parties. If the parties fail to do so in writing, but one party has fulfilled its main obligations and the other party accepts it, the contract is established.