The nine-digit Social Security number has been used since 1936 to track a person's wages for the purpose of accruing benefits within the Social Security Administration. Since its inception, the SSN
has become the unique identifier for a wide range of business processes. For example, the SSN is required for parents to claim their children as dependents for federal income tax purposes; the Internal Revenue Service requires all employers to obtain SSNs (or alternative identifying numbers) from their employees; the Navy and Marine Corps use the SSN on all military ID cards; and the SSN is used to access a variety of information technology system applications.
The SSN is Composed of Three Sections:
- The first three digits of the SSN are called area numbers. This is because they originally corresponded to the state that a person lived in at the time he or she was issued a SSN. Beginning in 1972, area numbers were assigned based upon the zip code in the
mailing address to which the individual requested his or her card be sent. In 2011, the geographical
significance of the first three digits of the SSN will be eliminated.
- Digits four and five in the SSN are referred to as group numbers. They are used to identify the block of numbers currently issued. As an example, the SSNs 123-01-0001 through 123-01-9999 would be issued before moving to the next group numbers.
- Digits six through nine are known as serial numbers. They are issued consecutively from 0001 to 9999.