here is an ex of why it is best to have the write off button on the done / payment screen.
I send colleague to knock on door to collect money, i say to him its say £32.00, later that day i say have you got the money he says yes heres £30, i say damn i told you it was £32.00 never mind,
I will not go back or mention this Shortfall to the customer, i just write it off and am more carefull next time, so when i get home,
i click job done ,
job paid £30.00
£2.00 written off