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Social Security Number Breakdown

What is a social security card and the number on it? A social security card is an important document that serves as an identification card and holds a unique number personal to you.

A social security number is one of the most important pieces of information about every person who has one—that is, most people who live and work in the US. While that much is pretty basic knowledge, what’s less clear is the significance of the numbers themselves.

Have you ever wondered: what do the numbers in your social security mean?

This guide will walk through everything you need to know about those nine important digits. We’ll go over what the numbers have meant historically and why they matter now.

What Do The Numbers Mean?

Often, the actual digits themselves in a social security number mean very little in terms of cryptography. There’s information hidden behind these numbers, but no major life-changing social security number codes to read into.

If it’s a newer number, chances are that the digits mean nothing at all. It’s just a number corresponding to a US citizen.

If it’s an older number, the digits may hint at some information about the person who owns them. But beyond age, that information is layered with contingencies that make it biographically insignificant. The number has to do more with how social security numbers were determined when it was assigned than with the people they’re assigned to.

How Are Social Security Numbers Determined?

Social security numbers are assigned today through a centralized and randomized process that both increases the longevity of the nine-digit system and safeguards the integrity of all existing numbers. New numbers are functionally random and insignificant code-wise. SSN randomization is a precautionary procedure that also works to prevent identity theft.

That said, it hasn’t always been that way; the numbers used to mean something.

Since the inception of the nine-digit system in 1936, there have been changes to the coded significance of each digit. Only one major factor has remained constant: the number is made up of three distinct strings of digits. Historically, these digits are coded as:

  • A three-digit Area Number
  • A two-digit Group Number
  • A four-digit Serial Number

The significance of these digits has changed meaningfully on two occasions:

  • Beginning in 1972, the Area Number was based on ZIP code
  • Beginning in 2011, all numbers have been randomized

Before getting into what randomization has meant for social security numbers, let’s go over what these digits and groupings have meant, historically. On a lesser note, all cards issued after 2007 also contain a date of issuance, so you can tell if a card is new. For all cards issued before 2011, these older specifications still apply.


Before the SSN randomization changes, which occurred on June 25, 2011, the nine digits on a person’s social security card were encoded with personal information. Each string of numbers was guaranteed to tell you something about the person it belonged to. However, that information itself was always somewhat tenuous and random.

It started with location:

Area Number

Between 1936 and 1972, the SSA assigned social security numbers from local offices throughout the country. The first three digits were tied to the office through which the card was applied for. As such, these numbers were intended to facilitate internal filing, not provide a historical record of the applicant.

Beginning in 1972, the SSA began to distribute cards centrally from the headquarters in Woodlawn, Maryland, just west of Baltimore. From this point onward, Area Numbers were allocated based on the ZIP code provided in an applicant’s mailing address. Individual states and locations were tied to particular sequences. For instance:

  • Numbers 001-576 are designated for the 50 states
  • Numbers 577-586 are for locations like Washington DC and the Philippine Islands
  • Numbers 700-728 were specially designated for rail workers until 1963
  • Certain numbers were designated “Not Issued” (000, 237-246, 666, etc.)

So, a social security number issued between 1972-2011 will typically tell you, at least, what mailing address a person used when applying for the card. That might not be where they lived at the time, but it often has some significance.

Group Number

A persistent myth about the Group Number is that it has some relation to a person’s racial background. This has no bearing in reality. The two-digit sequence is a sub-group within respective Area Numbers.

For each Area Number, there are 99 possible groups (01 to 99). But these were not assigned in that order. Instead, for administrative reasons, the allocation of Group Numbers worked like this:

  • Odd numbers first, from 01 to 09
  • Then even numbers, from 10 through 98
  • Finally, odd numbers from 11 through 99

In practice, this scheme meant that up until June 24, 2011, you could check to see what the highest Group and Serial Numbers were assigned up to date in the High Group History List. This enabled employers to see if a number provided to them had actually been assigned by the SSA. Looking up by given Group Number couldn’t tell you much else beyond whether a number was genuinely given to someone.

Of course, which individual Serial Number was given to each person is confidential.

Serial Number

Finally, the Serial Number is the last four digits of the social security number. A sub-sub-group within each Group Number within each Area Number, Serial Numbers were assigned consecutively, from 0001 to 9999. Before 1972, this set of number’s only determining factor was the order in which people applied for cards within the same location.

After 1972, it depended upon the sequence of applications within a given ZIP code. And since 2011, it has depended upon little but random number generation.


Since social security numbers are nine-digit sequences, there are just under one billion possible combinations. It stands to reason that every single possible number will be exhausted one day. With that being said, you might be wondering "Do social security cards expire?" However, they do not.

As far off as that day may be, restrictions on what numbers can be used pose limitations that jeopardize the longevity of the system. That’s why the SSA publicly declared in 2007 that it intended to randomize assignments. It finalized the changes in 2011.

As of 2011, the nine digits assigned in a social security number are completely random, except that no previously assigned nine-digit combination can be repeated. Some notable implications of this change include:

  • Area Numbers 000, 666, and 900-999 are now possible
  • So-called Area Numbers now have no bearing on the location
  • The High Group List is frozen

However, some things do stay the same. For instance, 00 is still an impossible Group Number, and 0000 is still an impossible Serial Number. The lowest number with the maximum number of zeroes now possible would be seven, in a number like 000-01-0001. But even that number wouldn’t tell you much about the person who it belongs to.

No matter how cryptically illegible these numbers are, they’re still incredibly important.

Why Do Social Security Numbers Matter?

For those assigned one at birth, the social security number marks one of the oldest pieces of identification they own. For others who obtained one later in life, it marks the beginning of a new phase of life here in the US.

A social security number is vital for many aspects of life, such as gaining employment and setting yourself up for retirement benefits.

A Ticket to Work

When you apply for a job in the US, you need to be able to prove that you are who you say you are—and that you can pay taxes. A social security number is what proves both of these things. That’s why employers typically ask to see a social security card when you apply for a job.

Your social security card functions as employee authorization and enables you to pay toward the fund that people’s social security benefits are drawn from. As long as you chip in or otherwise qualify, you too will be able to reap those benefits one day.

Your Access to Benefits

The main reason social security cards and numbers exist is to facilitate distribution of benefits to those who need them and those who’ve earned them. The various programs offered by the SSA provide income assistance and coverage for expenses for those unable to work for various reasons. The most important and prevalent include:

  • Retirement benefits
  • Disability benefits
  • Medicare benefits
  • Survivors benefits
  • Supplemental Security Income

Taken together, these social security benefits make up the safety net that supports all of society here in the US. The justification for the social security tax everyone pays on their income is that those funds given up now support others and, in turn, will support them too.

But to take advantage of these benefits, you need your social security number, located on your card. If something happens to that card, it’s extremely important to get it replaced as soon as possible.

For that, we’re here to help.

NYSS: Your Social Security One-Stop Shop

At NotYourSocialSecurity, our goal is to take the stress out of all things social security. That means explaining complex processes in-depth to empower you with knowledge and helping you find social security office locations near you. It also means providing easy, low-cost solutions for social security issues you run into.

If you need to replace a card that’s lost, stolen, or damaged, our E-Records tool is the best way to avoid waiting in line at your local social security office.

Replace your card from the comfort of your home with professional help you can trust.


SSA. A Myth About Social Security Numbers.

SSA. High Group History List.

SSA. Meaning of the Social Security Number.

SSA. Protecting the Integrity of Social Security Numbers.

SSA. Social Security Number Allocations.

SSA. Social Security Number Randomization.

SSA. Social Security Number and Card.

SSA. The SSN Numbering Scheme.

SSA. W-2 News, Issue 2008-04.