First of all, examine the subject signing the IOU to see whether both parties have full capacity for civil conduct and whether the subject is qualified. Secondly, among the IOUs generated by private loans, the purpose and use of the debt should be reviewed to find out whether the loan contract conceals illegal purposes in a legal form and whether there is any violation of mandatory provisions of laws and administrative regulations. and then determine the validity of the contract. Specifically, situations that may render a private loan contract invalid include: the lender knowingly knowing that the borrower will use the loan for illegal purposes but still providing the loan (such as providing loans to criminals to help them escape punishment, or knowing that the purpose of the loan is for illegal purposes) Gambling, drug abuse, and still providing loans, etc.);

(2) The lending relationship violates the national regulations on financial management (such as fund-raising fraud, illegal absorption of public deposits). Moreover, attention must be paid to the constituent elements of the IOU, and There is a clear and complete expression of meaning. Finally, in a lending relationship, it is necessary to examine whether the lender actually delivered the money. A loan contract between natural persons becomes effective when funds are provided.

Legal basis: Article 58 of the "General Principles of Civil Law" The following civil acts are invalid:

1. Performed by a person without capacity for civil conduct;

2. A person with limited capacity for civil conduct is unable to perform independently in accordance with the law;

3. One party uses fraud, coercion or takes advantage of others' danger to cause the other party to act against his true intention;

4. Malicious collusion to harm the interests of the country, the collective or a third party;

5. Violation of the law or social welfare interests;

6. Covering up illegal activities in legal forms purpose.