Legal analysis: printing IOUs has legal effect and is protected by law. Under normal circumstances, IOUs should be signed and fingerprinted. If the parties conclude a contract in the form of a contract, they shall sign or seal it. If the parties press their fingerprints on the contract, the people's court shall determine that it has the same legal effect as the signature or seal.

Legal basis: Article 490 of the Civil Code of People's Republic of China (PRC). If the parties enter into a contract in the form of a contract, the contract shall be 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.