depends where it is to be driven. different bodies have their own Licence CPCS (constructoion plant certification scheme) RTITB( road traffic Institute training board)
lots of companies have in house training which is only valid on their site.
many companies allow you to demonstrate that you can control the fork lift in a safe manner. they have courses designed to train drivers the proper and safe way to travel with a forklift and no load. then too, with a load. these will earn you not only a certificate, but a licence also. if O.S.H.A .ever requests proof of training and qualification, you will be required to show them.