If a IOU is written for a private loan, it shall be done in accordance with the provisions of the relevant written contract. According to regulations, the content of a loan contract generally includes terms such as loan type, currency, purpose, amount, interest rate, term and repayment method. If the parties agree in the guarantee contract that the guarantor and the debtor shall bear joint and several liability for the debt, it is a joint liability guarantee. When the debtor under a joint liability guarantee fails to perform the due debt or a situation stipulated by the parties occurs, the creditor may request the debtor to perform the debt or request the guarantor to assume the guarantee liability within the scope of its guarantee. Article 688 of the "People's Republic of China and Civil Code" If the parties agree in the guarantee contract that the guarantor and the debtor shall bear joint and several liability for the debt, it is a joint liability guarantee. When the debtor under a joint liability guarantee fails to perform the due debt or a situation stipulated by the parties occurs, the creditor may request the debtor to perform the debt or request the guarantor to assume the guarantee liability within the scope of its guarantee.