The IOU does not have to be signed by both husband and wife. 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 is better for both parties to sign it so as to determine it is a joint debt of husband and wife. According to the Civil Code of China, the debts incurred by the joint declaration of intention, such as the joint signature of both spouses or the subsequent ratification of one spouse, as well as the debts incurred by one spouse in his or her personal name for the daily needs of the family during the existence of the marriage relationship, belong to the joint debts of husband and wife.
 [Legal Basis]
 Article 1064 of the Civil Code of the People's Republic of China states that the debts incurred by the joint declaration of intention, such as the joint signature of both husband and wife or the subsequent ratification of one of the husband and wife, as well as the debts incurred by one of the husband and wife in the name of an individual for the daily needs of the family during the existence of the marriage relationship, belong to the joint debts of the husband and wife.
 The debts incurred by one of the husband and wife in their personal name during the existence of the marriage relationship in excess of the daily needs of the family are not joint debts of the husband and wife; However, unless the creditor can prove that the debt is used for the husband and wife's common life, production and operation, or based on the joint intention of the husband and wife.