Legal analysis: you can sue. According to the provisions of China's Civil Procedure Law, anyone who meets the conditions for prosecution can bring a lawsuit in court, but it is best to provide other relevant evidence, because if the IOU is not signed by the parties, the evidence will be weak and insufficient, and the case may not be won.

Legal basis: Article 119 of the Civil Procedure Law of People's Republic of China (PRC), the prosecution must meet the following conditions:

(1) The plaintiff is a citizen, legal person and other organization that has a direct interest in the case;

(2) Having a clear defendant;

(3) Having specific requests, facts and reasons;

(4) It falls within the scope of civil litigation accepted by the people's court and is under the jurisdiction of the sued people's court.

Article 121 A complaint shall contain the following items:

(1) The name, sex, age, nationality, occupation, work unit, domicile and contact information of the plaintiff, the name and domicile of the legal person or other organization, and the name, position and contact information of the legal representative or principal responsible person;

(2) Information such as the name, gender, work unit and domicile of the defendant, and information such as the name and domicile of the legal person or other organization;

(3) the request and the facts and reasons on which it is based;

(4) Evidence and its sources, names and residences of witnesses.