How do you know I’m a twin?

How did the Twin Registry get my name and contact information?

We work in partnership with the Washington State Department of Licensing (DOL) to identify twins. To ensure that each member of a twin pair receives a different license number, the DOL asks every applicant if he or she is a twin on applying for a new or renewed driver’s license or state ID card. We received permission from the Washington State Attorney General under the Driver Privacy Protection Act (US Code 18, Section 2721) to receive contact information for all applicants who say they are twins.

Unfortunately, we have no way of knowing ahead of time if an individual actually is a twin, or if they have a living twin. Our invitations are not meant to cause worry about identity theft, insult, or any negative feelings about having lost a twin or not being in contact with a twin. If you receive an invitation and you are not a twin, do not have a living twin, or are not interested in participating, be sure to let us know right away so that we do not mail to you in the future.

We keep your name and contact information completely confidential and never share it with anyone outside of the Twin Registry without your permission.

Why didn’t my twin also receive an invitation to join the Twin Registry?

If you recently applied for or renewed your driver’s license or state ID card through the Washington State Department of Licensing (DOL), we received your name and contact information, and sent you an invitation. If your twin did not apply for a driver’s license or state ID card at around the same time, we did not receive your twin’s name and contact information. This is why you received an invitation to participate, but your twin did not.

Occasionally the Washington State DOL will give us information for both twins. However, because the DOL does not tell us which license applicants are related to one another, we still ask all potential participants to provide their twin’s information.

Why does the Washington State DOL ask about twins?

The Washington State Department of Licensing (DOL) is unique in that it encodes your last name, first and middle initial, and your date of birth in your driver’s license or identification card number. Based on this formula, twins have the potential to generate the same license number. These license numbers look like the following:


  • LLLLL – Last Name, truncated – The first five characters are the first five letters of the last name. If the name is shorter than five characters, the extra space is padded with asterisks (*).
  • F – First Initial
  • M – Middle Initial
  • YY – Year of birth, encoded – This is 100 minus the two digit year of birth. So someone born in 1998 will be 02 (100-98), as would someone born in 1898.
  • X – Checksum – calculated from the rest of the license
  • Month of Birth, encoded:
  • Day of birth, encoded:twinday

Based on this formula, the following is an example of a twin pair that could have the same license number:

    • WOO**JT547KA
      • “John T. Woo,” born on May 1st, 1946
    • WOO**JT5462A
      • “Joe T. Woo,” born on May 1st, 1946

To avoid issuing a duplicate driver’s license number, the DOL asked both John & Joe if they are a twin. John was the first twin to request a license from the DOL, so his month of birth is encoded with the character from column 1, above. Joe was the second twin, so his month of birth is encoded with the character from column 2. The DOL compiles a list of these names on a weekly basis and forwards them to the Twin Registry. Invitations are sent out on a monthly basis.

Occasionally twinship is indicated accidentally by the DOL. In these instances an individual may receive an invitational packet when they are not actually a twin. Unfortunately, we have no way of knowing ahead of time if someone is in fact a twin. If you received an invitational packet and you are not a twin, please send us an email and let us know.