Certificate of conformity for a trailer or caravan

Category O in four classes

Towed vehicles form category O in European type-approval law, alongside passenger cars (M) and commercial vehicles (N). It is subdivided by gross vehicle weight:

Class	Gross vehicle weight	Common examples
O1	up to 750 kg	small luggage trailer, motorcycle carrier
O2	750 kg to 3.5 t	caravan, horsebox, flatbed trailer
O3	3.5 t to 10 t	professional trailer
O4	over 10 t	semi-trailer

The class governs the braking system required and the registration regime. It appears on the certificate of conformity alongside the gross weight and the dimensions.

Where to find a trailer’s chassis number

A trailer has neither engine nor windscreen, but it does carry a 17-character identification number. It is usually:

• stamped or engraved on the drawbar, at the front of the chassis;
• repeated on the manufacturer’s plate riveted to the chassis or inside a locker;
• written on the registration document of the country of origin, where one exists.

On a caravan the plate is often placed in the gas locker or near the entrance door. On older trailers it may have been painted over: a rag and a little patience are usually enough to make it legible again.

What the certificate changes when you hitch up

The certificate does not merely describe the trailer: it carries the figures that determine what you are allowed to tow. Gross vehicle weight, unladen weight, maximum nose weight — these combine with the figures for the towing vehicle, themselves taken from its certificate of conformity.

That is why it is useful to have both documents consistent when the combination is to be used regularly. The licence categories applicable to a combination depend on the country of registration: check with the competent authority.

What about specialist trailer brands?

Our price list covers car manufacturers. Trailers and caravans are built by specialist makers who are not in that table: they are handled case by case, and the price is confirmed to you before anything is started.

If your trailer was sold under the badge of a car manufacturer present in our list, the channel is the same as for a vehicle. See all brands.