Legal analysis: An IOU is a valid IOU if it meets the following conditions:

1. The interest agreement complies with legal regulations.

2. Both the creditor and the debtor have full capacity for civil conduct.

3. The IOU is the true expression of intention of both parties.

4. The content of the IOU does not violate the law or public interests, does not infringe upon the legitimate interests of a third party, and does not violate the mandatory provisions of the law.

Legal basis: "The People's Republic of China and the Civil Code"

Article 667: The loan contract means that the borrower borrows money from the lender and returns the loan and pays when due interest contract.

Article 668: A loan contract shall be in written form, unless otherwise agreed upon for a loan between natural persons.

The content of a loan contract generally includes terms such as loan type, currency, purpose, amount, interest rate, term and repayment method.

Article 669: When entering into a loan contract, the borrower shall provide the true situation of business activities and financial status related to the loan as required by the lender.