SSN

The SSN, or Social Security number, is a nine-digit number issued by the United States Social Security Administration to U.S. citizens, permanent residents, and certain noncitizens for records and identification within the Social Security program as well as many other systems.

The number is written as XXX-XX-XXXX and comprises three parts: the area number (AAA), the group number (GG), and the serial number (SSSS). The SSA previously tied areas to geographic regions, but since 2011 randomization allows any valid number. Certain values are invalid: 000-00-0000; area 666 and 900-999 not issued; group 00 invalid; serial 0000 invalid.

Issued by the SSA, most people receive an SSN at birth or when they immigrate. It is used for employment eligibility checks (I-9), tax reporting (W-2, 1040), and to access government benefits and many private sector services such as banking and credit. It is not intended to serve as a universal national ID, but it is widely used as an identifying key.

Established in 1936 as part of the Social Security program to track earnings and determine benefits, the SSN system was later used for payroll tax withholding and various government programs. In 2011, the SSA introduced randomization of SSN assignments to improve security and privacy and to reduce geographic linkage of numbers.

Because the SSN is highly sensitive, improper disclosure can lead to identity theft. Laws like the Privacy Act regulate how it is collected and used by government agencies; employers, financial institutions, and other entities often require a legitimate need to see the number. Individuals are advised to limit sharing and safeguard documentation; replacements and corrections can be requested through the SSA.