1. The IOU can be signed by one or both of the borrower's husband and wife. If both husband and wife know about the loan, it's best for both parties to sign it, so as to confirm that the husband and wife are in debt together. The limitation period for requesting protection of civil rights from the people's court is three years. Where there are other provisions in the law, those provisions shall prevail.

2. Legal basis: Article 490th of the Civil Code of People's Republic of China (PRC).

If the parties enter into a contract in the form of a contract, the contract shall be established when the parties sign, seal or press their fingerprints. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it.

A contract shall be concluded in written form as stipulated by laws, administrative regulations or agreed by the parties. If the parties do not do this in writing, but one party has fulfilled its main obligations and the other party accepts it, the contract is established.

Second, how to write IOUs has legal effect.

When writing an IOU, it shall have legal effect if it has the following contents and meets the legal requirements:

1. Names and ID numbers of borrowers and lenders;

2. The amount, date, term, repayment date and interest of the loan;

3. The borrower shall sign and fingerprint.

3. Which IOUs are invalid?

The following IOUs are invalid:

1. The IOU used for illegal purposes is invalid, that is, the lender knows that the borrower borrows money for gambling, smuggling and other illegal activities, and its lending relationship is not protected;

2. The IOU signed by the person in danger or forced state is invalid;

3. The IOU without actual payment is invalid;

4, malicious collusion, damage to the interests of the state, the collective or the third party IOUs are invalid.