Drivers must carry and complete the diary when working more than 100 kilometres from base (or under certain fatigue schemes regardless), and operators must retain the records and check them for breaches. Failing to keep, or falsifying, a work diary is an offence for the driver and often for the operator.
The electronic form is the electronic work diary. The practical duties, and what evidence an operator should hold, are in the fatigue and work diaries guide.
General information, not tax or legal advice.