Overview#Social Security Number (SSN) in the United States is a nine-digit National Identification Number issued to U.S. citizens, permanent residents, and temporary (working) residents under section 205(c)(2) of the Social Security Act, codified as 42 U.S.C. § 405(c)(2).
Social Security Number is issued to an individual by the United States Social Security Administration, an independent agency of the United States federal government. Although its primary purpose is to track individuals for Social Security purposes, the Social Security number has become a de facto national identification number for taxation and other purposes.
Social Security Number may be obtained by applying on Form SS-5, Application for A Social Security Number Card.