Legal analysis: A legal and valid loan IOU should clearly define the subject, object, and content of the IOU, express it clearly, and pay attention to avoid ambiguity. The amount unit should be clear, the amount should be written in capital Chinese, and the ratio should be Clarify the percentage, thousandth and ten thousandth ratio, and the return date. It is best to have two copies of the receipt, with each party holding one copy.

Legal basis: "Provisions of the Supreme People's Court on Several Issues Concerning the Application of Law in the Trial of Private Lending Cases" Article 9 If a loan contract between natural persons falls under any of the following circumstances, it may be deemed to be established:

(1) If it is paid in cash, when the borrower receives the loan (2) When it is paid in the form of bank transfer, online electronic remittance, etc., when the funds arrive in the borrower's account (3) When it is delivered by bill, When the borrower obtains the rights to the bill in accordance with the law (4) When the lender authorizes the borrower to have control over a specific fund account, when the borrower obtains the actual control over the account (5) The lender provides the loan in other ways agreed with the borrower and when actual performance is completed.

Article 13 If any of the following circumstances occurs, the people's court shall determine that a private loan contract is invalid: (1) obtaining a loan from a financial institution and (2) obtaining a loan from a financial institution. Borrowing money from other profit-making legal persons, raising funds from employees of the unit, or on-lending funds obtained by illegally accepting deposits from the public (3) Lenders who have not obtained lending qualifications in accordance with the law provide loans to unspecified objects in society for the purpose of profit (4) The lender knew or should have known in advance that the borrower's loan was used for illegal and criminal activities but still provided the loan; (5) It violated the mandatory provisions of laws and administrative regulations; (6) It violated public order and good customs.