Legal analysis: If the IOU does not include interest, and if there is no agreement on the payment of interest in the loan contract, it will be deemed that there is no interest. The borrower and the lender have not agreed on interest in the loan contract. Even if the lender demands that the other party pay interest, the people's court will not support it. Therefore, if interest is not written on the IOU, there is no interest on the loan between the two parties.

Legal basis: Article 680 of the "People's Liberation Army and Civil Code of the People's Republic of China" prohibits usury lending, and the interest rate for borrowing must not violate relevant national regulations.

If the loan contract does not stipulate the payment of interest, it will be deemed that there is no interest.

If the loan contract does not clearly stipulate the payment of interest, and the parties cannot reach a supplementary agreement, the interest shall be determined according to the local or parties’ transaction methods, transaction habits, market interest rates and other factors; for loans between natural persons, it shall be deemed that there is no Interest.

Article 24 of the "Regulations of the Supreme People's Court on Several Issues Concerning the Application of Law in the Trial of Private Lending Cases" If the borrower and the lender have not agreed on interest, and the lender claims to pay interest, the People's Court will not support it.

If the interest agreement on a loan between natural persons is unclear and the lender claims to pay interest, the people's court will not support it. Except for loans between natural persons, if the loan interest agreement between the borrower and the borrower is unclear and the lender claims interest, the people's court shall determine the interest rate based on the content of the private loan contract and the local or parties' transaction methods, transaction habits, market quotation interest rates and other factors. Interest.