Suffix registrations came into effect in 1963. They follow a specific format of three letters at the start, followed by one, two or three digits and are completed by a suffix letter at the end, which acts as an age identifier. It is the final year identifying letter that earns this style of registration its name. An example of a typical suffix number plate is RMS 27D and this particular plate identifies the year of manufacture as 1966. Originally, the first three letters of a suffix plate identified the area where the vehicle was registered. The numbers on suffix registrations only act to differentiate between vehicles with the same prefix and suffix letters.

The suffix registration system commenced with A in 1963 and changed annually, all the way through to Y, which indicated 1982. The suffix letters I, O and U were not used as age identifiers, while a Q registration indicates that the year or origins of a vehicle are uncertain.

It is possible to transfer a suffix registration onto your vehicle, but as with all age identifiable registration plates, you can only assign a suffix registration mark to a vehicle manufactured in the same year or before. It is not possible to use a suffix registration to make your vehicle appear more recent than it actually is. You can, of course, use a private number plate to make your vehicle appear older than it is. With regards to the example registration mark, RMS 27D, this could only be assigned to a vehicle manufactured from 1966 onwards.