Trailer registration is not required for trailers used in the UK or between the UK and Ireland and trailers for private use internationally. However from March 2019, it will be mandatory for all commercial use trailers travelling internationally that weigh over 750kg in gross weight ( category 02). Registration is also mandatory for non-commercial use trailers that travel internationally and weigh over 3500kg in gross weight (03).
Other trailers that weigh over 750kg in gross weight can be registered on a voluntary basis even if they are not travelling abroad. Registration will be valid for 10 years.
Apart from the registration certificate, number plates must be made up and displayed in a visible and vertical position on the trailer. This is separate to the existing number plate of the vehicle pulling the trailer.To date, DVLA states that there is no requirement to illuminate the trailer registration plate.
The trailer’s number plate must be fixed as far as reasonably possible from the towing vehicle’s registration plate. If the plate cannot be displayed at the rear of the trailer, a trailer registration plate must be fixed to both sides of the trailer so they are both clearly visible.
It is recommended to also display the UK’s recognised distinguishing sign GB
Trailers can be registered on the DVLA web site, you will need the name of the manufacturer, the trailer vin number, the gross weight and the un laden weight.