In order to use jobs to track your "profit centers," you'll enter information about the job and assign a job number to the job. You'll then enter the job number on transactions to track the net profit (loss) for the job.
You can set a preference to display a reminder if one or more of the line items on a transaction don't have a job assigned to them, if you wish. When you receive the reminder, you'll have the option of recording the transaction as is or of returning to the transaction and assigning a job to every line. (System view of the Preferences window)
Step by step