Legal analysis: As a legal document to prove the existence of creditor-debtor relationship between the two parties, the validity of IOUs depends on whether the debts are legal or not. If the debt owed is illegal, such as gambling debt owed due to gambling, the debt is illegal. Although the debt owed by the debtor is signed by the debtor and the guarantor, it still has no legal effect, and the creditor has no right to pay the corresponding debt according to the debtor's debt, nor has it the right to ask the guarantor to bear the guarantee responsibility.

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.