Expiration date

In some states, the month of expiration or the county of registration is incorporated into the plate's serial. The last number on a Massachusetts license plate indicates the month the vehicle's registration expires (for example, 1234 AB would expire in April, the fourth month; 0 indicates October expirations; and X and Y were used for November and December expirations, respectively, on commercial plates and pre-1978 passenger plates). The same applies to the first number or letter on West Virginia plates (1 to 9 for January through September, and O, N, and D for October, November, and December expirations, respectively). Additionally, the first letter of Missouri passenger plates denotes the month of expiration. The month's position within the calendar year corresponds to the letter's position within the alphabet; i.e. the letters progress from "A" and "B" for January to "Y" and "Z" for December.

County of issuance

In Alabama, Montana, Nebraska, South Dakota, and Wyoming, a one- or two-digit number representing the county of issue begins a license plate number. Standard-issue Idaho license plate numbers begin with a single-letter or a number-letter code representing the county of issue; for example, vehicles registered in Ada County start with 1A, vehicles in Twin Falls County start with 2T, and vehicles in Valley County start with V (as there is only one county that starts with the letter V). County codes have been based on historical population figures, the county names in alphabetical order, or some combination thereof. In Montana, for example, the county codes were assigned around 1930 and have not changed since.^[3] Other states like Indiana and Tennessee also once used the practice, with Tennessee discontinuing in the 1980s and Indiana in 2008.

Four jurisdictions in the United States use letters to designate a residence where a vehicle was registered. In Hawaii, the license plates have a unique letter designation based on the island counties that residents purchased or registered the vehicles from; a vehicle with a registration number beginning with H or Z is registered in Hawai‘i County, one beginning with K is registered in Kaua‘i County, one beginning with M or L is registered in Maui County, and one beginning with any other letter (and not containing H, K, L, M, or Z) is registered in the City and County of Honolulu. In the U.S. territory of Guam, the license plates use the first two letters that are coded by village of issuance, for example, "TM-1234" refers to a vehicle that was registered by a person who lives the village of Tamuning. In the U.S. Virgin Islands, a vehicle with a registration number beginning with C is registered in St. Croix, J in St. John, and T in St. Thomas.

Several states do require vehicles to display county codes, but these codes are not part of the serial. Indiana and Ohio display two-number county codes, while Kansas plates display two-letter county codes, but these codes are placed on a sticker or are printed in the corner of the plate in a smaller font size. Texas places the county name only on the windshield registration sticker, where the car's license plate number is also printed. Florida, Georgia, Iowa, Kentucky, Mississippi, Ohio, and Tennessee place the full name of the county of registration explicitly on their standard-issue plates, although not as part of the serial. However, Florida allows its residents to choose either "Sunshine State" or "In God We Trust" in place of the county name, and Georgia allows drivers to choose the slogan "In God We Trust" in place of the county name.

Skipping characters

For various reasons related to visibility and readability, some states and territories exclude certain letters from use in their license plate serial formats. The most commonly skipped characters are I, O, and Q^{[citation needed]}, with some states using only one or two of the three while others will skip all three of these letters^{[citation needed]}. Other states, such as Colorado, Georgia, and South Carolina have gradually adopted one or more of these letters over a course of years after previously skipping them in order to accommodate the demands of population growth and depletion of available serial combinations. The most common argument behind skipping I, O, and Q is that they can be too easily confused with 0, 1, and other characters, particularly when there isn't adequate spacing or divider between numbers and letters^{[citation needed]}.

California only uses I, O, and Q in between two other letters, for example "1AQA000".^{[citation needed]} A unique example of character use is Texas, which skips all vowels along with the letter Q on passenger plates.

In amateur radio license plate issues, some states use a unique slashed zero character in place of the standard "0" character due to lack of spacing between letters and numbers. Iowa is a unique example in the use of this character, which began using the slashed zero beginning in 2012 on all standard passenger plates as opposed to the traditional symbol for zero to differentiate it from the letter "O" which is also used. In Pennsylvania, the die used for the number "0" is different than the one used for the letter "O" since the state's number dies are taller and narrower than its letter dies.

Persons with disabilities

In the states, special plates displaying the International Symbol of Accessibility are issued to persons with disabilities that entitle them to special parking privileges. Alternately, a placard, which in some jurisdictions can be hung from the rear view mirror, may be issued; the placard has the advantage of being transferred from vehicle to vehicle.