1. Loans made five years ago can be supplemented by IOUs. An IOU is a written document indicating the relationship between creditor's rights and debts, which is generally written and signed by the debtor, indicating that the debtor has owed the creditor the amount indicated in the IOU. It is a bill written to the other party when borrowing personal or public cash or goods.

2. Legal basis: Article 668 of the Civil Code of People's Republic of China (PRC).

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.

Second, what problems should I pay attention to when borrowing?

1. There must be a written loan contract or loan note. Indicate the loan date, loan amount, loan interest rate and repayment date in detail. If the interest agreement is not clear or there is no agreement, it is deemed that there is no need to pay interest. The loan contract must be signed by both parties, and the loan note must be written by the borrower himself. If there is a guarantor, the responsibilities of the guarantor should be clearly written together and signed by the guarantor himself. In addition to signature, it is best for the borrower to confirm by fingerprint;

2. Interest can be agreed, but it must be legal. Private lending can only require the borrower to pay interest when repaying the principal if both parties agree in advance in writing or orally that it is an interest-bearing loan; Otherwise, it is regarded as an interest-free loan, and the lender may not require the borrower to pay interest;

3. Borrowing can require the borrower to provide mortgage or guarantee. The mortgage or guarantee provided by the borrower adds an insurance for the recovery of the loan, and even if the borrower cannot repay it, he can still claim compensation from the guarantor.