You will need to complete a PCV Category D1 training course and test if you would like to get your category D1 minibus licence in order to be able to drive minibuses with up to 17 seats (including the driver seat) and obtain an income from driving minibuses for hire and reward.

If you passed the Category B Car test before January 1997 and you already have a Category D1 entitlement on your driving licence, but with a code restriction 101 next to it, you can drive a minibus for private, non-commercial use. 

But if you would like to drive a minibus for hire and reward (ie as a job, to earn money for it etc.), then you must sit and pass the D1 minibus test.