What size minibus can I drive?

The size of a minibus is determined by its weight (Maximum Authorised Mass or MAM) and this in turn relates to the number of passenger seats.
Drivers who only have B or B(120) entitlement are the only ones who need to check the weight of the minibus. It does not affect other drivers.
You will find a plate on the minibus that is sometimes called the chassis plate or VIN plate. It may be in the door frame, in one of the front foot wells or under the bonnet.
The relevant weight is always the second biggest weight on the plate. On a standard 17 seat Ford Transit minibus it would be 4100kg. It would be illegal for a driver with only B entitlement to drive this minibus (4100kg) as the maximum MAM they can drive is 3500kg for a standard minibus or 4250kg if the vehicle is adapted with specialist accessible equipment, e.g. a tail lift.

Further information can be obtained through the Driving a Minibus on the DVLA webpages https://www.gov.uk/driving-a-minibus