Social Security Number - Purpose and Use

Purpose and Use

The original purpose of this number was to track individuals' accounts within the Social Security program. It has since come to be used as an identifier for individuals within the United States, although rare errors occur where duplicates do exist. As numbers are now assigned by the central issuing office of the SSA, it is unlikely that duplications will ever occur again. A few duplications did occur when prenumbered cards were sent out to regional SSA offices and (originally) Post Offices. Employee, patient, student, and credit records are sometimes indexed by Social Security number. The U.S. Armed Forces has used the Social Security number as an identification number for the Army and Air Force since July 1, 1969, the Navy and Marine Corps since January 1, 1972, and the Coast Guard since October 1, 1974. Previously, the United States military used a much more complicated system of service numbers.