Since 1 May 2006 all new goods vehicles over 3.5 tonnes and minibuses with the ability to carry 10 passengers including the driver are legally required to be fitted with a digital tachograph.
If you are planning to hire a vehicle fitted with a digital tachograph for commercial use you will need to have a valid Driver Card. You will also need a Driver Card if you are driving a minibus abroad, whether for private or commercial use.
Further information can be found at the FTA website.