The fraudulent use of a social security number is a crime under both federal and state law. One agency charged with the responsibility of investigating potential fraud and prosecuting those found guilty of committing this crime is the Social Security Administration's Office of the Inspector General (OIG). Reporting potential fraud involving social security numbers is one way to play an active role in reducing the incidence of identity theft, which plagues many --- the Federal Trade Commission received as many as 278,078 identity theft complaints, not including other white-collar offenses, in its Computer Sentinel Network in 2009.
Obtain the identifying information of the person you suspect of committing the fraud. This includes his name, contact phone number and social security number, if possible. According to the Social Security Administration, "if the SSN is unknown, include as much identifying information as possible."
Write a letter addressed to "Social Security OIG Hotline" providing as much detail as possible regarding the potential fraud. If you would like to remain anonymous in the course of OIG's investigation of the alleged incident, be sure to make mention of that in your letter.
Mail your letter to the Social Security OIG Hotline. If you prefer to report the alleged crime online, complete the Fraud Reporting form.
Answer any inquiries that the Social Security OIG may have pertaining to the potential fraud. Generally, after the Social Security OIG receives your complaint, they will confirm receipt of your letter. Depending on whether you chose to remain anonymous, the Social Security OIG may use your testimony without disclosing your identity, or require you to testify in a court of law.