There is no need for both husband and wife to sign the IOU. One party may entrust the other party to sign it, or after one party signs it, the other party will ratify it afterwards. Debts signed by both husband and wife or ratified by one party afterwards are valid for both husband and wife.

Legal objectivity:

Article 161 of the Civil Code of People's Republic of China (PRC) * * * A civil subject may carry out civil juristic acts through an agent. Article 1064 of the Civil Code of People's Republic of China (PRC) * * * Debts incurred by both husband and wife with the same signature or later ratified by one of the husband and wife, and debts incurred by one of the husband and wife in his own name for the daily life of the family during the marriage relationship belong to the same debt of the husband and wife. Debts incurred by one spouse in his own name during the marriage relationship that exceed the needs of family daily life are not joint debts of husband and wife; However, the creditor can prove that the debt is used for the husband and wife's life, production and operation, or based on the same meaning of both husband and wife. Article 1089 of the Civil Code of People's Republic of China (PRC) * * * In case of divorce, the husband and wife shall jointly pay off their debts. * * * If the same property is not paid off or the property belongs to each other, it shall be paid off by mutual agreement; If the agreement fails, the people's court shall make a judgment.