We currently use AP,AR and GL. When we implement job costing will we have a field in AP,AR,GL to pick the job number, phase etc. that the Revenue or cost relates to when entering invoices into Accounts Receivable,Accounts Payable or journals in the Ledger?

Yes to AP and AR, no to GL. There would be no reason to code a journal entry to a job. However, you can accomplish the same thing by entering a batch directly in the JobCost module, selecting a GL account as the offset.

Steve