https://www.gov.uk/towing-with-car/driving-licence-rules-and-what-you-can-tow

The rules on what you can tow are different depending on when you passed your driving test.

Licences issued from 19 January 2013

From 19 January 2013, drivers passing a category B (car and small vehicle) test can tow:

• small trailers weighing no more than 750kg
• trailers weighing more than 750kg, where the combined weight of the towing vehicle and the trailer isn’t more than 3,500kg Maximum Authorised Mass (MAM)

If you want to tow a trailer weighing more than 750kg, when the combined weight of the towing vehicle and trailer is more than3,500kg, you’ll have to pass a further test and get B+E entitlement on your licence.

You’ll then be able to tow trailers up to 3,500kg.

Licences held from 1 January 1997

If you passed your driving test after 1 January 1997 and have an ordinary category B (car) licence, you can:

• drive a vehicle up to 3.5 tonnes or 3,500kg MAM towing a trailer of up to 750kg MAM
• tow a trailer over 750kg MAM as long as it is no more than the unladen weight of the towing vehicle (with a combined weight of up to 3,500kg in total)

Licences held before 1 January 1997

If you passed your car test before 1 January 1997 you are generally entitled to drive a vehicle and trailer combination up to 8.25 tonnes MAM.

This is the weight of a vehicle or trailer including the maximum load that can be carried safely when it’s being used on the road.

You also have entitlement to drive a minibus with a trailer over 750kg MAM.

Towing heavier combinations

If you want to tow heavier combinations, you’ll have to first apply for provisional entitlement to the new C1+E entitlement. You’ll then have to pass the category C theory test and C1+E practical test.

Once you’ve done this you can drive vehicles and trailers with a combined weight of up to 12 tonnes MAM.