QB is not good at job costing in my experience. QBO is worse and QB Payroll makes even harder.  I am sure someone will pipe in here to tell you some complicated convoluted way to do this in QB so hopefully you get the help you need.  My suggestion is a different system that does job costing as it should not be from payroll, it should be from timesheet where you allocate gross labor not net pay.  Please feel free to contact me if you need to do true job costing, like for Govt contracts as I must do.