No third-party signature is required for IOUs. If the parties conclude a contract in written form, the time of formation of the contract is the time when both parties sign or seal it. Therefore, the loan contract is established when both parties sign or seal it. When the borrower/debtor writes down the IOU and signs his own name, the IOU has been established and has legal effect, and does not need the signature of a third party. Legal basis: Article 667 of the Civil Code? A loan contract is a contract in which the borrower borrows money from the lender, repays the loan at maturity and pays interest. Article 668 of the Civil Code? 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.