The Social Security Administration determines your Social Security number by computer, and since June 25, 2011, it does so at random. A program pulls a nine-digit number from the pool of numbers still available, without reference to your state, your ZIP code, or when you applied. If you’re wondering how they determine your Social Security number today, that’s the whole mechanism: an algorithm picks, the number is assigned to you for life, and nothing about the digits reveals anything about you.
Numbers issued before mid-2011 were determined differently, and that older method still explains most of what people notice about SSNs they’ve seen over the years.
What the Nine Digits Represent
Every SSN is written in a three-two-four pattern, and the SSA has names for each piece:
- The first three digits are the Area Number.
- The middle two digits are the Group Number.
- The last four digits are the Serial Number.
That format has been the same since the first cards were issued in 1936. What changed in 2011 is the logic behind which digits land in which slot.1Social Security Administration. Social Security Numbers – The SSN Numbering Scheme
How the Number Is Determined Now
On June 25, 2011, the SSA moved to what it calls Social Security Number Randomization. A computer algorithm assigns each new number from the entire available pool, and the three segments no longer carry any information about the person receiving them.2Social Security Administration. Social Security Number Randomization
Two babies born in the same hospital on the same day now receive numbers with no relationship to each other. The Area Number no longer signals a state. The Group Number is no longer part of any issuance cycle. The Serial Number is not sequential within anything. It’s all random within the ranges the SSA is allowed to use.
The SSA has given three reasons for the switch. Randomization removes the link between the digits and personal facts like geography, which had made SSNs easier to guess. It also spreads new numbers across the full pool instead of burning through the blocks assigned to high-population states, which extends how long the nine-digit format can keep going. And it retires the geographic meaning of the Area Number entirely, so the old “High Group List” the SSA once published is now frozen and only useful for checking numbers issued before mid-2011.2Social Security Administration. Social Security Number Randomization
Numbers the Algorithm Will Never Pick
Randomization doesn’t mean anything goes. Several ranges are permanently excluded and can’t be assigned:
- Any number with all zeros in a segment. A number with 000 in the first three positions, 00 in the middle two, or 0000 in the last four is invalid.3Social Security Administration. Social Security is Changing the Way SSNs are Issued
- Any number with an Area Number of 666. This prefix was blocked well before randomization and remains blocked.
- Any number with an Area Number in the 900–999 range. The IRS uses that range for Individual Taxpayer Identification Numbers (ITINs), which go to people who need to file taxes but don’t qualify for an SSN.3Social Security Administration. Social Security is Changing the Way SSNs are Issued
A “Social Security number” that starts with 000, 666, or a 9 is either fake or an ITIN. The assignment system won’t produce one.
How Numbers Were Determined Before June 2011
For most of the program’s history, every segment of the number was doing real work.
The Area Number came from geography. Before 1972, it reflected the specific Social Security field office where you applied. Starting in 1972, when the SSA centralized processing in Baltimore, the Area Number was drawn from the ZIP code on your mailing address instead.1Social Security Administration. Social Security Numbers – The SSN Numbering Scheme Either way, the first three digits pointed to a state, and people who applied from the same place tended to share similar Area Numbers.
The Group Number was an internal sorting tool, and it cycled through in an odd order rather than running straight up. Within each area, the SSA used odd numbers 01 through 09 first, then even numbers 10 through 98, then even numbers 02 through 08, and finally odd numbers 11 through 99.4Social Security Administration. Social Security Bulletin The SSA published a High Group List so employers and agencies could see which group numbers had already been issued in any given area, which helped flag suspicious numbers.5Social Security Administration. Employer Filing Instructions and Information – SSN Order of Issuance
The Serial Number was the straightforward part. Within each area-group combination, it ran from 0001 through 9999. When 9999 was reached, the SSA moved to the next Group Number in the cycle.5Social Security Administration. Employer Filing Instructions and Information – SSN Order of Issuance
That predictability was the problem the SSA eventually solved with randomization. Researchers showed that knowing someone’s birth state and rough date of birth was often enough to guess large portions of their SSN.
How the Number Reaches You
The algorithm has to be triggered by an application. There are three usual routes.
Enumeration at Birth
Most Americans get their SSN within weeks of birth without their parents ever going to a Social Security office. Under the Enumeration at Birth program, parents request a number during hospital birth registration. The state’s bureau of vital statistics sends the birth information to the SSA electronically, and the SSA assigns a number, issues a card, and updates its records automatically.6Social Security Administration. What is Enumeration at Birth and How Does it Work The birth certificate worksheet at the hospital covers age, identity, and citizenship, so no separate SSA form is needed.7Social Security Administration. State Processing Guidelines for Enumeration at Birth
Applying With Form SS-5
If you weren’t enrolled at birth, you apply on Form SS-5. You’ll need documents in three categories: proof of age, proof of identity, and proof of U.S. citizenship or work-authorized immigration status.8Social Security Administration. Application for a Social Security Card
- Proof of age is usually a birth certificate. The SSA may also accept a U.S. hospital birth record created at the time of birth, a religious record from before age five, or a passport.
- Proof of identity is typically a U.S. driver’s license, state ID, or U.S. passport. If you don’t have those, the SSA can accept alternatives such as a military ID, school ID, or health insurance card that shows your legal name and biographical details.
- Proof of citizenship is usually a U.S. birth certificate or U.S. passport. Naturalized citizens can use a Certificate of Naturalization or Certificate of Citizenship.
All documents must be originals or certified copies from the issuing agency. Photocopies and notarized copies are not accepted. There’s no fee.8Social Security Administration. Application for a Social Security Card
Noncitizens
Noncitizens generally need work authorization from the Department of Homeland Security before the SSA will issue a number. Accepted immigration documents include the Permanent Resident Card (Form I-551), the Arrival/Departure Record (Form I-94), and the Employment Authorization Document (Form I-766).9Social Security Administration. Social Security Numbers For Noncitizens If you’re applying for an immigrant visa from outside the United States, you can request an SSN as part of the visa application and skip the trip to a Social Security office.
Noncitizens without work authorization can only get an SSN if they can show a valid non-work reason, such as a state law requiring the number to receive a public benefit. That usually means a letter from the government agency asking for the number.9Social Security Administration. Social Security Numbers For Noncitizens
Whichever route triggers the assignment, the same randomization algorithm picks the digits. Once assigned, the number is yours for life, and the SSA does not reuse it after the holder’s death.