To hold stock for customers on your premises, add a new stock location, ie. CON.
Transfer the stock to that stock location.
Add a new status of Consign.
Add a new job from the consignment location and use the status of Consign.
If you wish to send a document to the customer listing the consignment stock, you can create a copy of a Picking Slip via Report Designer, and change the name of the report:
