Is the receipt an iou?

Not an iou. The IOU is the proof of the relationship between creditor's rights and debts, and the receipt is the proof of receiving money and materials. The legal relationship between them is different, and receipts cannot replace IOUs.

Legal basis:

People's Republic of China (PRC) Civil Code

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.