Legal analysis: it is impossible for only one party to sign the iou. Whether it is valid or not depends on whether the signatory is the borrower. There are several situations in which IOUs are not established:

1. The borrower fails to sign the receipt for confirmation;

2. Both parties have no real borrowing facts;

3. The debt is illegal, and the debt IOUs that are not protected by law must be filled out by the debtor himself. Some debtors used to find someone to write the IOUs for them in order to avoid their debts. When creditors demanded money back, they refused to pay back on the grounds that it was not their own handwriting. Therefore, the IOU must be filled out by the debtor himself. If the IOU is printed, it is best to ask the borrower to sign, stamp and fingerprint the borrower's signature column.

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

Article 667 A loan contract is a contract in which the borrower borrows money from the lender, repays the loan at maturity and pays interest.

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

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

Article 669 When concluding a loan contract, the borrower shall, at the request of the lender, provide the true information about the business activities and financial status related to the loan.