Hidden inside all those numbers on your Illinois driver's license is a secret code that gives away some personal details about you.

Illinois Driver's License

When a driver’s license is given out, most states give you a unique number that can be used to identify you. The state gives you a driver’s license if you can drive on public roads. Most of the time, this license has the driver’s license number written on it.

In some states, the number on your driver's license is your social security number, but in other states, there are different rules at play.

In Illinois, your driver's license has a code hidden inside all of those numbers and it reveals your:

  • Name
  • Gender
  • Birthdate

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This is how the secret code was broken down for me to understand. We'll start by removing the hyphens from your driver's license number and writing it out like this.

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That first letter is the first letter of your last name, then those three numbers are the Soundex Code of your last name. The Soundex is a coded surname index (using the first letter of the last name and three digits) based on the way a name sounds rather than the way it's spelled.


Encoded first name and middle initial. There are codes used for your first name and if your name isn't on the list, and there are many names not included, you then use a number based on the first letter of your first name.


Year of birth


Day and month of birth and your gender.

This one is determined by the sex and the month and day of birth. The formula for IL is:

(Birth month minus1) x 31 + Day of birth + (600 if female, 0 if male)

For example, if you were born on April 3, 1977, and are male you would compute:

(04-1) x 31 + 03 + 0 = 93 + 3 = 96. So his DDD number is 096.


If your Illinois driver's license number has more than 11 numbers and one letter, then the NN is for overflow numbers to differentiate those who could have the same license number.

Putting the hyphens back in, and an Illinois driver's license looks like this:


An Illinois driver's license looks like this:


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You'll find the name and initial charts used for encoding here, and how other states determine their driver's license numbers, here.

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