A legal IOU should have four elements: what the borrower saw and when to return it; Borrowers and lenders should indicate their ID numbers and loan purposes. Finally, both sides need to stamp. If there is a guarantor, it also needs his signature and seal.

Specific details include the loan amount, which needs to be case-sensitive. The two parties clearly agreed on the repayment period of the loan, the calculation standard of interest within the loan period, the responsibility for overdue repayment and the calculation of overdue interest, and finally signed the full name. The real name cannot be omitted or only written. Finally, the borrower should sign and fingerprint, indicate the date of loan and valid ID number.

"IOU" refers to the creditor's rights certificate issued by the debtor to the creditor when the borrower establishes the rights and obligations relationship with the borrower, and can also be signed under the witness of a lawyer. IOUs help protect creditors. Only the IOUs drawn up and signed and sealed according to these factors can have legal protection.