If there is any doubt about the authenticity of IOUs, the following methods are generally adopted: First, verify the actual flow of funds. In economic exchanges, any capital flow will inevitably lead to financial traces. Especially for large cash flows, both enterprises and individuals generally involve financial institutions such as banks. If the parties deposit and withdraw money in the bank, then the bank will have receipts and payments. Therefore, the judge can investigate and verify the relevant finances according to the application, or ask the parties to provide relevant settlement vouchers. Second, make comprehensive judgments and form inner conviction. When the evidence presented by both parties is "equivalent" or uncertain, and it is difficult to judge whether the loan really exists based on some important evidence, the judge should give full play to his subjective initiative, restore the truth as much as possible, and make a comprehensive judgment according to the parties' ability to pay, trading habits, previous cooperative relations, loan amount and other factors to form inner conviction. Third, technical appraisal. Technical appraisal is the most direct and effective method to judge the authenticity of IOUs. Usually, forged IOUs include forged IOUs, forged time, forged signature, forged fingerprints and so on. The obligee can identify the IOUs through judicial authentication, including bill authentication, IOUs generation time authentication, fingerprint authentication and so on.