Generally, there are two situations:
1. One is that the borrower is forced to write an IOU, not the borrower's own borrowing behavior, so in this case, the IOU has no legal effect.
2. The second is that if the IOU is your own behavior, you deliberately write the wrong name or don't write your own name in order to avoid responsibility, then the IOU is equally effective.
According to the relevant laws of our country, a contract is deemed invalid under several circumstances:
1. The contract was signed by one party under the coercion of the other party, not by both parties voluntarily.
2. The IOUs signed by both parties deliberately collude to harm the relevant interests of the state, the collective or others.
3. Any violation of relevant laws and regulations of our country is regarded as invalid contract.