Writing an IOU is legally valid, and the following conditions need to be met: 1. Both parties signing the IOU are persons with full civil capacity; 2. The content of the IOU must be legal and valid, which generally includes: the reason for the debt, the amount and interest of the debt, the time and method of repayment, and the responsibility for breach of contract and dispute resolution mechanism. According to the relevant laws and regulations in China, a loan contract is a contract whereby the borrower borrows money from the lender, returns the loan and pays interest when due. According to the relevant laws and regulations of our country, the loan contract should be in written form, except that the loan between natural persons is otherwise agreed. The contents of a loan contract generally include terms such as the type, currency, purpose, amount, interest rate, term and repayment method of the loan.
 How long is the validity period of the IOU?
 1. Provisions on the validity period of the IOU: the IOU is subject to the ordinary limitation of action, that is, the limitation period of action is 3 years.
 2. The term of validity of the IOU marked with the repayment date is 3 years, starting from the repayment date indicated in the document; The term of validity of the IOU without agreed repayment date is also 3 years, but it is calculated from the establishment of the debt relationship between the two parties.
 To sum up, do you have a certain understanding of how to write a debit note with legal effect? Article 667 of the Civil Code? A loan contract is a contract whereby the borrower borrows a loan from the lender, returns the loan and pays interest when due.
 Article 668 of the Civil Code? A loan contract shall be in writing, except where the loan between natural persons is otherwise agreed.
 The contents of a loan contract generally include terms such as the type, currency, purpose, amount, interest rate, term and repayment method of the loan.