Legal analysis: IOU is legally defined as a loan contract, which is a practical contract and requires the actual delivery of the loan. After the loan is delivered, the loan contract is valid as long as it does not violate the mandatory provisions of national laws; However, because nicknames are written and cannot directly indicate who the borrower is, there may be obstacles when defending rights. If you sue, you need to clarify the borrower's information!

Legal basis: Civil Code of People's Republic of China (PRC).

Article 196 A loan contract is a contract in which the borrower borrows money from the lender, repays the loan at maturity and pays interest.

Article 197 A loan contract shall be in written form, unless otherwise agreed between natural persons.

The contents of the loan contract include the loan type, currency, purpose, amount, interest rate, term and repayment method.

Article 198 When concluding a loan contract, the lender may require the borrower to provide a guarantee.