Your entitlement to tow large trailers depends on when you passed your car test. With a car (category B) only licence, you are still able to tow something, but with weight restrictions applied.
Unfortunately, the wording on the gov website can be a little confusing so hopefully the information below will help.
* Anything shown as "E" on your driving licence relates to trailers within that category - i.e. BE (also referred to as B+E) means car (B) plus trailer (E) *
NOTE: - If you have also passed additional higher category driving tests, this may have "upgraded" your driving and / or towing entitlements in the lower categories (see further down below under "Licence Upgrades").
Full Category B (Car) licences obtained before 1st January 1997
The gov website wording for this category obtained up to 31st December 1996 is -
"You’re usually allowed to drive a vehicle and trailer combination up to 8,250kgs maximum authorised mass (MAM). You’re also allowed to drive a minibus with a trailer over 750kgs MAM".
The 8,250kgs MAM figure is a little misleading here. Given that this description is under Category B, it is implying that this weight relates to Category B. The upper limit of 8,250kgs MAM actually relates to the Category C1 which was also automatically given to those who passed their car test before 1st January 1997.
C1 = Vehicles between 3,500 and 7,500kg MAM (with a trailer up to 750kg). 7,500 kgs + 750 kgs = 8,250 kgs
The good news is that those who passed their car test before 1st January 1997 were given full B+E entitlement automatically (acquired rights) and can tow any large trailer providing you are adhering to the towing capacity of the vehicle you are towing with - (Construction & Use Regulations apply here).
Full Category B (Car) licences obtained on or after 1 January 1997
The gov website wording for this category obtained from 1st January 1997 is -
You can drive vehicles up to 3,500kgs MAM with up to 8 passenger seats (with a trailer up to 750kg). You can also tow heavier trailers if the total MAM of the vehicle and trailer isn’t more than 3,500kgs.
**There was also an addition that the weight of the trailer must not exceed the unladen weight of the vehicle. However, this wording was removed around January 2013.**
This means you can tow a trailer up to 750kgs behind any category B vehicle or tow a heavier trailer providing the MAM weight of the vehicle plus the MAM weight of the trailer added together does not exceed 3500kgs.
If your vehicle already has a MAM weight of 3,500kgs - The maximum plated MAM weight of a trailer you can tow is 750kgs on a category B only licence.
If your vehicle has a MAM weight of 2,500kgs - The maximum plated MAM weight of a trailer you can tow with this vehicle on a category B only licence is 1,000kgs. Towing capacity of the vehicle must also not be exceeded.
In 2013, a further amendment was made to the B+E category to introduce an upper weight limit of the trailer to 3,500kgs with a total maximum train weight of 7,000kgs.
The gov website wording is -
The maximum weight of a trailer you can tow on a B+E licence now depends on the BE "valid from" date shown on your driving licence.
Before 19th January 2013, you can tow any size trailer
On or after the 19th January 2013, you can tow a trailer with a MAM up to 3,500kgs
In reality, the upper trailer limit does not affect most drivers passing their B+E on or after 19th January 2013 as it is extremely rare to find a category B vehicle with a towing capacity above 3,500kg.
The few "specially modified" category B vehicles that can legally tow above 3,500kg would be affected and so can only be used to tow to their maximum towing capacity by a driver who obtained their B+E prior to this 2013 change.
If you have passed a higher category driving test since 1st January 1997, some lower categories may have been upgraded on your licence.
Just two examples are:
If you already hold a full licence for categories B & C1, passing the C1+E test automatically upgrades your licence to include B+E.
If you already hold a full licence for categories B & D1, passing the D1+E test automatically upgrades your licence to include B+E.
This is because you have demonstrated competence in driving a bigger and heavier vehicle / trailer combination by passing the relevant test, so B+E (being a lower size and weight category) has been automatically added.