The short answer
Add the maximum authorised mass of the towing vehicle and that of the trailer. Up to 3,500 kg class B is enough. Above 3,500 and up to 4,250 kg you need B96. Above that, BE. Both figures are the maximum authorised masses from field F.1 — not what the scales actually show.
This calculation is got wrong more often than anything else around driving licences — and the mistake only surfaces at a roadside check, when it gets expensive.
The calculation
- Maximum authorised mass of the towing vehicle — registration certificate part I, field F.1
- Plus the maximum authorised mass of the trailer — its own field F.1
- = maximum authorised mass of the combination
Up to 3,500 kg class B is enough. Between 3,500 and 4,250 kg you need B96. Above 4,250 kg you need BE. A trailer up to 750 kg is always allowed, whatever the sum.
The most common mistake
Using the kerb weight instead of the maximum authorised mass. Until the start of 2013 the towing vehicle's kerb weight did play a role; that rule no longer exists. Today only the maximum authorised masses count — what the vehicles are permitted to weigh, not what they weigh empty.
Loading changes nothing
An empty horsebox has the same maximum authorised mass as a full one. For the licence question it makes no difference whether you drive loaded — and “but there was nothing in it” is not an argument at a check.
An example
A mid-size estate with a maximum authorised mass of 2,100 kg and a caravan at 1,500 kg makes 3,600 kg. Over 3,500, so class B is not enough — with B96 it fits. The same estate with a two-horse trailer at 2,400 kg makes 4,500 kg: over 4,250, so BE.
What you can do when it is close
Some trailers can be re-rated up or down — the maximum authorised mass is changed and re-registered. Rating down can bring a combination under a threshold, but it also reduces what you may load. Whether that makes sense depends on what you actually transport.
Bring both registration certificates to the first consultation and we will work it through with you. Which of the two classes follows is covered in BE or B96.