Legal analysis: legally effective. According to legal provisions, as long as the signer has the corresponding civil capacity and is signed by himself, his signature will be legally valid. As for the font used by the signer to sign, it will not affect the legal effect of the signature itself. Of course, for insurance purposes, the borrower's fingerprints are usually required. The borrower's signature is acknowledgment of the written content, and such an IOU is valid.

Legal basis: "The People's Republic of China and the Civil Code"

Article 667: The loan contract means that the borrower borrows money from the lender, and returns the loan and pays when due interest contract.

Article 668: A loan contract shall be in written form, unless otherwise agreed upon for a loan between natural persons.

The content of a loan contract generally includes terms such as loan type, currency, purpose, amount, interest rate, term and repayment method.

Article 669: When entering into a loan contract, the borrower shall provide the true situation of business activities and financial status related to the loan as required by the lender.