Otherwise, the other party will hint that he just inadvertently wrote his name on a piece of white paper, and all the debts were filled in by others.

This may eliminate the probative effect of IOUs.

If the other party really can't write, then there must be two or more people who have no interest relationship between the two sides to testify (write references: XXX, XXX ...).

Of course, it also depends on the amount owed. If there are only a few hundred dollars, the other party is really decent and has little to do with it. If it is tens of thousands of yuan, the loan should be cautious and rigorous to prevent disputes.