Situation:
Customer is on a contract and has pre-paid hours. A job takes 1 hour and no hardware is supplied, so only 1 pre-paid hour should be deducted. There is no need for an invoice because it would just create a zero charge invoice and that creates paperwork for no reason.

Solution:
Have the option to deduct the hours at the ticket level when the hours are 'charged' using a Labour line item.

This allows for the ticket to be used to track prepay hours usage on both sides - customer and admin.