Are you job costing customer invoices before you cost the inventory records?

 If so, you may be crediting inventory in the General Ledger with a lower or higher cost that actually posted to the General Ledger from the accounts payable record.

If this system option is set to yes,

then you can job cost an order with inventory that is not costed.

If you decide this is not what you want to do, RFMS will give you a warning at the time of costing inventory that this inventory record has been assigned to a customers' order and job costed. You will then have to go to order entry, search for the job, un-job cost it, un-assign the line, re-assign the line so it will pick up the correct cost for job costing, re-job cost the job.