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Social Security Number Format | What Do The Numbers Mean?

Social Security Cards For Identification Stacked On Eachother

Most people have their Social Security number memorized, or they at least know where to find their SSN. This number is critical for identification purposes, and you need to have it whenever you attempt to get a loan, open a bank account, or perform many other services. Most people never really think about the structure of the Social Security number itself. You might know that it is nine digits, but do you know why the number is separated the way it is? Also, do you know the significance and meaning of each section of your SSN? If not, keep reading as we give you all the details on the formatting of Social Security numbers.


Social Security Number Format

Social Security Number Format Diagram

The Social Security number format is a nine-digit number, generally separated by hyphens into sections of three digits, two digits, and four digits. For example, a typical SSN follows the format of “AAA-GG-SSSS,” where A represents the Area number, G represents the Group number, and S represents the Serial number. The format of the numbers has been relatively unchanged since the assignment of the first Social Security numbers back in 1936.

Contrary to popular belief, Social Security numbers are not assigned in consecutive order. The process used by the Social Security Administration (SSA) to assign SSNs has changed a couple of times over the years. Up until 1972, numbers were assigned by Social Security field offices. The field office in your geographic area would assign your SSN. Since 1972, all numbers have been assigned by the central office at the Social Security Administration. While it is hard to obtain details about the order in which numbers are assigned, information is available about what each section of numbers means. We will discuss the significance of each group of numbers in the next sections of this article.

Area Number

The first section of three digits of your SSN is the area number. Some people also call this the Social Security number prefix. This number is associated with a specific geographical location. Similar to ZIP codes with the post office, area codes for your SSN started in the Northeast and worked westward. This means that folks in the Northeast had lower numbers than those on the West Coast. Again, the process change in 1972 also affected how area numbers were assigned. After 1972, the area number was assigned based on the ZIP code of the mailing address on your Social Security card application.

Since these numbers are based on the mailing address provided on the application, this means that the assignment is not necessarily based on the location of a person’s permanent residence. Someone might live in one state but temporarily have their mailing address in another state. So, you cannot necessarily use an SSN to determine where someone lives. Plus, since most people are assigned an SSN at birth, they might move many times over the course of their life.


Group Number

The middle section of two digits of a valid SSN is the group number. The group number is a way of breaking the areas into smaller sections, although the group number is not associated with a specific geographic area. Instead, the group numbers are assigned in a specific order for each particular area. First, the odd numbers 01 to 09 are assigned. Next, even numbers from 10 to 98 are assigned. Then, even numbers 02 through 08 can be used, and finally, odd numbers from 11 to 99 will be assigned. The number “00” is never used for the group number.

Each month, the Social Security Administration publishes a report that shows the highest group number assigned for a specific area number. For example, if the report shows that the highest group number for a certain area is 68, then you know that 72 or 13 is not a valid group number for that area since the numbers are assigned in order following the rules above.

Serial Number

The last group of four digits in your SSN is known as the serial number. The serial numbers are assigned strictly in chronological order per area and group number. It is worth noting that this does not always seem to be the case before 1965 when field offices assigned numbers. Then, there appeared to be more randomization as some groups of serial numbers seemed to be assigned out of order. However, today, the assignment of a serial number for each area and group starts at “0001” and continues upward to “9999.” Note that “0000” is never a valid serial number. In fact, any group of all zeros is never a valid number in any section of an SSN.

You might think that you could look at a person’s SSN and determine their age. However, that is not always the case. Serial numbers are assigned based on the time at which an application is received, and not everyone applies for a Social Security number at birth. Issuance of an SSN for some people may occur well into adulthood, while others may be assigned a few weeks after birth.


Social Security ‘Area Code’ Number Chart

You can find a full listing of area codes along with their associated geographic region on the Social Security Administration website. Remember that the area codes are not simply limited to the 50 United States. American citizens born in U.S. territories may also request a Social Security number, so the regions must include these locations as well. Here are all the Social Security area codes, along with which region they are associated with.

You might notice that some area numbers are included in more than one region. This means either that the number was transferred from one region to another or that it is used in more than one area.


Social Security Number & Geographic Region

Area NumberGeographic LocationArea NumberGeographic Location
001-003New Hampshire478-485Iowa
008-009Vermont501-502North Dakota
035-039Rhode Island505-508Nebraska
050-134New York516-517Montana
135-158New Jersey518-519Idaho
221-222Delaware525, 585New Mexico
232North Carolina528-529Utah
232-236West Virginia530, 680Nevada
237-246Not Issued531-539Washington
247-251South Carolina540-544Oregon
303-317Indiana577-579District of Columbia
318-361Illinois580Virgin Islands
362-386Michigan580-584Puerto Rico
400-407Kentucky586American Samoa
408-415Tennessee586Philippine Islands
416-424Alabama587-665Not Issued
425-428Mississippi667-679Not Issued
429-432Arkansas681-690Not Issued
433-439Louisiana691-699Not Issued
440-448Oklahoma700-728Railroad Board
449-467Texas729-733Enumeration at Entry
468-477Minnesota750-772Not Issued


The Bottom Line

Many people think that a Social Security number is just nine random numbers that get assigned by the Social Security Administration. However, that is not the case. Each section of numbers in an SSN has a specific purpose, and you can use those numbers to determine certain things about when and where the number was assigned. You can even use the details of each section to determine whether a number might be invalid.


Frequently Asked Questions

What is the maximum number of digits in a Social Security number?

The maximum number of digits in a Social Security number is nine. This is also the minimum number of digits. Every valid SSN is nine digits and follows the format of “AAA-GG-SSSS.” The three sections represent the area number, the group number, and the serial number of the SSN.

What is the last digit of a SSN?

The last digit of an SSN could be any digit from zero to nine. The last four digits are called the serial number. Serial numbers are assigned in ascending order from “0001” to “9999” for each area number and group number. There is no specific meaning to the last digit on its own; however, you can use the entire serial number to estimate the time period in which the SSN was assigned.

How are the first three digits of your Social Security number determined?

The first three digits of your SSN are determined by the mailing address on your Social Security card application. This does not necessarily mean that your number is associated with where you live. Your mailing address might temporarily be different than your permanent residence, although the first three digits of your SSN often indicate the location where you were born.