Contracts usually need to be signed by both parties. This kind of signature is generally understood as signature or seal, and the private seal is a simplification of the signature and has the same effect as the signature. Article 32 of the Contract Law stipulates that if the parties conclude a contract in the form of a contract, the contract is established when both parties sign or seal it. For legal persons or other organizations, the official seal is required. According to the provisions of the contract law, if the official seal is affixed without the signature or seal of the legal representative or responsible person or his authorized agent, the contract is still valid. The General Principles of Loans stipulates that the guarantee contract needs the official seal of the legal person and the signature or seal of the legal representative or person in charge or its authorized agent, but the General Principles of Loans is a stipulation, which is not as effective as the Contract Law. Article 1 1 of the Measures for Payment and Settlement stipulates: "The signatures on bills and settlement vouchers are signature, seal or signature and seal. The signature of the unit or bank on the bill and the signature of the unit on the settlement voucher are the signature of the unit or bank plus the signature of its legal representative or its authorized agent. The signature and seal of the individual on the bill and settlement voucher shall be the signature or seal of the real name of the individual. " Article 4 1 of the Provisions on Several Issues Concerning the Trial of Bills Disputes stipulates that the drawer's signature and seal on a commercial bill shall be the special financial seal or official seal of a legal person or unit plus the signature or seal of its legal representative, person in charge of the unit or its authorized agent. The signature of the drawer of the bank draft and the signature of the acceptor of the bank acceptance draft are the special seal for the bank draft plus the signature or seal of its legal representative or its authorized agent. However, if the bill is stamped with the official seal instead of the special seal, the signatory shall also bear the bill liability according to the provisions of Article 42. The signature on the bill is stricter than that in the contract law, and it needs the signature or seal of the legal representative or his authorized agent.