The letters “DD” on a driver’s license stand for Document Discriminator. It’s a unique number assigned to the specific physical card in your hand, used by state motor vehicle agencies and law enforcement to verify that the card is genuine and current. It has nothing to do with your health, your driving record, or any restriction on your privileges.
Every time you get a new card, whether through renewal, replacement, or a name change, a new DD number is generated. Your license number stays the same. The DD changes.
What the Document Discriminator Is
The American Association of Motor Vehicle Administrators (AAMVA) sets the design standards that all states follow. Under those standards, the document discriminator is a number that “must uniquely identify a particular document issued to that customer from others that may have been issued in the past.”1AAMVA. AAMVA DL/ID Card Design Standard 2020
Your license number identifies you as a person. The DD identifies the specific piece of plastic. If you lose your wallet and get a replacement, your license number is unchanged, but the new card carries a new DD. The old DD is retired. Any attempt to use the lost card after it’s been reported missing will show a mismatch when scanned.
Where to Find It on the Card
The DD is printed on the front of the card, though the exact spot varies by state. AAMVA standards put it in the lower portion of the front face.1AAMVA. AAMVA DL/ID Card Design Standard 2020 Some states label it clearly as “DD,” others spell out “Document Discriminator,” and a few just print the number in small type near the bottom edge without any label at all.
If you can’t find it on the front, look for a long alphanumeric string that isn’t your license number and isn’t a date. The DD is also encoded in the PDF417 barcode on the back of the card, which is what most ID scanners actually read.
How the DD Differs from Your License Number
These two numbers do different jobs, and mixing them up is common.
- Your license number is tied to you. It follows you across renewals and replacements and is used to pull up your driving record, verify your identity, and link you to insurance and registration records.
- The document discriminator is tied to the card. It changes every time a new card is printed and is used to confirm that the card you’re holding is the current valid one.
The AAMVA standard is explicit: if the same DD appears on more than one card, it has failed its purpose.1AAMVA. AAMVA DL/ID Card Design Standard 2020 Each one has to be unique to a single issued card.
Why the Number Exists
The document discriminator is a fraud-prevention tool. It works in two main ways.
It catches counterfeits. A fake ID might carry a plausible license number, but a bar, airport, or retailer running the barcode through a scanner will see whether the encoded DD matches an actual card issued by the state. A card that was never really printed by the state won’t have a valid DD in the system, and the scan fails.
It also flags outdated cards. When you renew or replace your license, the old card is supposed to go away. The DD tells the system which version is current. If someone runs your old card, whether that’s a police officer at a traffic stop or a business verifying your ID, the DD reveals that a newer card has since been issued.
When Someone Will Ask for Your DD
Most drivers never think about the DD until a form asks for it. A few situations where it comes up:
- State tax filing. Some state e-filing systems require your DD to help verify your identity and cut down on fraudulent returns. If the number on your card is worn or hard to read, this is where you’ll notice.
- Online ID verification. Services that verify your identity electronically sometimes ask for the DD in addition to your license number, as a second confirmation that you’re holding a real, current card.
- After a replacement. Once a new card is issued, the old DD is invalidated. The old card looks the same and carries the same license number, but it’s no longer valid for identification.
If a form asks for your DD and you can’t locate it on the card, your state’s motor vehicle agency can tell you where to look. Placement and labeling vary enough that a call is often faster than hunting.
DD Is Not a Restriction or a Medical Code
People sometimes assume “DD” refers to a medical condition, and diabetes comes up often. It doesn’t. Driver’s license restriction codes are separate markings that indicate conditions on your driving privileges. Common examples include “B” for corrective lenses, “G” for daylight driving only, and “C” for mechanical aids. These codes vary by state, and none of the standard restriction systems use “DD” for a medical condition.
If you have a health condition that affects your driving, any restriction your state places on your license will appear in a different field and use a different code. The document discriminator carries no information about your health, your driving record, or your privileges. It’s a card-security number, nothing more.