What letter is used on UK registration plates for vehicles whose age or identity is in doubt?

Vehicle registration plates (VRP) are the mandatory alphanumeric plates used to display the registration mark of a vehicle, and have existed in the United Kingdom since 1903. It is compulsory for motor vehicles used on public roads to display vehicle registration plates, with the exception of vehicles of the reigning monarch used on official business.

The ‘Q’ shows that the vehicle was either not originally registered in the UK and proof of age was unavailable at registration, or that it has been built using a significant proportion of used parts.

If a vehicle has to be rebuilt, say after an accident and many new or used parts have been used that it calls the identity of the vehicle into question, the vehicle needs to be registered on a ‘Q’ Plate. This is done through the DVLA. It does not mean that there is anything wrong with the vehicle, just that it’s original identity cannot be clarified from the parts it is made from (i.e. from different vehicles).

Kit cars usually have a Q registration and this is perfectly normal, but on other vehicles, it suggests that their full history may be difficult to trace.