Are all Social Security Numbers (SSNs) valid? What is the composition of the SSN?

Validity of SSNs:

  • Not all SSNs are valid. Specific numbers are flagged as invalid for various reasons, which include:
    • Special Areas:
      • Areas 700-728: Used for Railroad Workers until 1964.
      • Areas 900-998: Reserved for internal SSA programs.
      • Areas 675-699 & 729-899: Reserved for future SSA use.
    • Advertisement & Promotions:
      • SSNs ranging from 987-65-4320 to 987-65-4329: Reserved for ads.
      • SSN 219-09-9999: Used in a 1940 SSA pamphlet.
      • SSN 078-05-1120: Sample card used by a wallet manufacturer in 1938, which has been falsely used by over 40,000 people.

Composition of the SSN:

The nine-digit SSN has three distinct parts:

  1. Area Number (First 3 digits):

    • Originally represented the state where the card was issued.
    • Post-1972, it's based on the ZIP code from the application's mailing address.
    • Area Numbers aren't strictly indicative of an applicant's state of residence.
    • Numbers generally increased from east coast (lowest) to west coast (highest).
  2. Group Number (Middle 2 digits):

    • Ranges from 01 to 99.
    • Odd numbers from 01-09 were issued first, followed by even numbers from 10-98 for each Area Number.
    • Post all assignments in an area, even groups 02-08 are used, then odd groups 11-99.
    • Before June 25, 2011, a "Highest Valid Group" list was maintained. SSNs issued after this date through random assignment made this list redundant. Our DMF service issues warnings if an SSN's Group number rank surpasses the highest rank before June 25, 2011.
  3. Serial Number (Last 4 digits):

    • Runs consecutively from 0001 to 9999 within each group.