Legal analysis: There is no restriction on the paper used in IOUs by law, so the paper used in IOUs in reality is also more casual. It is best to choose writing paper, that is, it will not scratch or spread when writing; Try to choose blank paper to avoid confusion between existing handwriting or printed words and the contents of the loan; Try to choose paper with long storage time to avoid oxidative damage after a long time.

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.