Why are some number plate ranges not available on prefix number plates?
The ranges of numbers DVLA make available on prefix plates depends on the registration date, and whether or not they were sold on new vehicles at the time. The number ranges have changed over the years. Here is a table showing how the registration numbering works on prefix plates, if the number you want isn’t here, you can’t have it. This might change over time however as DVLA can, if they wish, make unused numbers available.