Handwritten certificates are generally legally binding. Handwritten certification materials are legally effective if they meet the following conditions: one party's intention is true; Signature of the second party in person; Prove that the content does not violate the law; Third, as long as the facts of the case can be proved, they can be used as evidence. At the same time, evidence needs to meet three standards: authenticity, legitimacy and relevance. From the perspective of legal risks, it is suggested to keep the original written documents in order to protect the rights and interests of the parties in case of disputes.