As already said a decent notepad will do,1 thing record everything you do on the day might seem a bit OCD but truck reg,trailer time started finished,breaks where you went when and what time you finished.
if you got diesel how much where you stopped hours worked and how many hours break you had between shifts.
And anything different eg delayed at customer 1 or 2 due to load not ready etc.
If a week or 2 later gaffer said you were rude,late or didnt turn up to a customer you can look in your notes and tell him,if you say err dont remember gaffer will take customers word over yours due to keep customer happy and can get another driver not a customer.
Have my last 3 note books when i was at poundland start times trucks etc and hours worked,ok i dont need em now but was always did if it came to it.
(dont need em now?? well class 1 is an itch once you have driven you have to scratch it time for a few agency phone calls dammit lol sometimes big trucks diesel and doing a proper job just gets too much to watch em drive about all day time i was back in the saddle ).