The three parts of your Social Security number

Your Social Security number has nine digits divided into three sections: the area number (first three digits), the group number (middle two digits), and the serial number (last four digits). Each section was assigned for a specific reason, though the system has changed over time.

The Social Security Administration (SSA) issued these numbers starting in 1936 to track earnings and benefits. Understanding what each part represents helps you recognize a legitimate card and spot common mistakes on documents that ask for your number.

Key Takeaways

  • The first three digits (area number) originally indicated the state where you applied for your card, though this is no longer true for cards issued after 2011.
  • The middle two digits (group number) have no geographic or personal meaning — they were assigned in a specific order as the SSA processed applications.
  • The last four digits (serial number) are straightforward sequential numbers assigned to complete your unique identifier.
  • Since 2011, the SSA has randomized all nine digits, so you cannot determine where someone applied for their card based on the number alone.

The area number: what the first three digits meant

Before 2011, the first three digits corresponded to the state where you applied for your Social Security card. For example, cards issued in Connecticut started with 001 through 003, while cards issued in California started with 545 through 573. This made it possible to guess roughly where someone had applied based on their number.

The SSA stopped using this system in June 2011 and began randomizing all nine digits. Today, the first three digits have no geographic meaning. If your card was issued before 2011, the area number may still reflect where you applied, but if it was issued after 2011, it does not. This change was made to reduce identity theft, since criminals could no longer predict valid Social Security numbers based on location.

The group number: what the middle two digits mean

The middle two digits have never had geographic or personal significance. They were assigned in a specific order as the Social Security Administration processed applications. The SSA used group numbers to organize the workload — they would issue numbers in blocks to different processing offices.

Group numbers range from 01 to 65, 67 to 99 (the number 66 was never used). Before randomization, knowing the area and group number together could narrow down roughly when someone applied for their card, but this is no longer possible since all digits are now randomized.

The serial number: what the last four digits mean

The last four digits are the serial number, which straightforward counts from 0001 to 9999. Once the SSA assigned all serial numbers within a particular area and group combination, they would move to the next group number. There is no hidden meaning in these digits — they are purely sequential.

These four digits are the most commonly used part of your Social Security number in everyday life. Banks, employers, and government agencies often ask for or display only the last four digits when confirming your identity, since the full nine-digit number is considered sensitive information.

How randomization changed the system in 2011

On June 25, 2011, the Social Security Administration stopped assigning numbers based on geography and sequence. Instead, they began randomizing all nine digits. This means that a Social Security number issued today tells you almost nothing about where the person applied or when.

The randomization was intended to make Social Security numbers harder to predict and guess. Before 2011, someone with basic information about you could sometimes construct a plausible Social Security number. Randomization closed that vulnerability. If you received your card before June 2011, your number still reflects the old system; if you received it after, all nine digits were randomly assigned.

What Social Security numbers never include

Certain digit combinations are never issued as Social Security numbers, even under the randomization system. The SSA does not issue numbers with all zeros in any section (000-00-0000), numbers with 666 in the area section (666-xx-xxxx), or numbers with 900 or higher in the area section (900-99-9999 and above). These restrictions exist to prevent confusion and maintain the integrity of the system.

If you see a Social Security number that violates these rules, it is not a valid number. This can be useful if you are checking whether a number on a document looks legitimate, though the only way to confirm a number is actually valid is through the Social Security Administration itself.

Why this information matters for your records

Understanding how Social Security numbers are structured can help you spot errors on your own documents. If a bank statement, tax form, or government letter shows your Social Security number incorrectly, you can catch it and report it. Errors on official records can affect your earnings history and benefits later.

You should also know that your Social Security number is sensitive information. While the structure is public knowledge, your actual nine-digit number should be kept private. Only share it with employers, financial institutions, government agencies, and healthcare providers who have a legitimate reason to request it.

Frequently Asked Questions

Can I tell what state someone is from based on their Social Security number?

Only if their card was issued before June 2011. For cards issued after that date, no — the SSA randomized all nine digits, so the area number no longer indicates location. Even for older cards, the area number shows only where they applied, not necessarily where they lived.

What does it mean if a Social Security number starts with 666?

It is not a valid Social Security number. The SSA has never issued numbers with 666 in the area section. If you see this on a document, it is either a typo, a placeholder, or a fraudulent number.

Can I change my Social Security number?

The Social Security Administration can issue you a new number in limited situations, such as if your number has been stolen or if you are experiencing harassment or abuse. You would need to contact your local Social Security office and provide documentation of the reason. A new number does not erase your old earnings record — the SSA links both numbers to your account.

Why does my Social Security number start with 000 or 666?

You should not have a valid Social Security number starting with these digits. If a document shows your number this way, contact the Social Security Administration or the organization that issued the document to report the error. It may indicate a data entry mistake or a fraudulent record.

Does my Social Security number reveal my birth date?

No. Your Social Security number contains no information about when you were born. The nine digits are either geographically and sequentially assigned (for cards issued before 2011) or completely randomized (for cards issued after 2011), but neither system encodes birth date information.