Based on the Wikipedia spec:
^[A-Z]{2}[ -][0-9]{1,2}(?: [A-Z])?(?: [A-Z]*)? [0-9]{4}$
- The first two letters of the registration plate represent the State in which the vehicle is Registered.
- The next two digit numbers are the sequential number of a district. Due to heavy volume of vehicle registration, the numbers were given to the RTO offices of registration as well.
- The third part is a 4 digit number unique to each plate. A letter(s) is prefixed when the 4 digit number runs out and then two letters and so on.
- In some states (such as the union territory of Delhi, and the state of Gujarat) the initial 0 of the district code is omitted; thus Delhi district 2 numbers appear as DL 2 not DL 02.
- The National Capital Territory of Delhi has an additional code in the registration code: DL 01 C AA 1111