Which UPC code are you referring to? The one that is enterable on the Inventory master item?

Looking at the 'plnItems' database list within the PO designer, I don't see UPC code available - probably as it is not used nor stored on the purchase order document. I suspect that UPC is not available for PO's.

The specfiication designer in OrderEntry allows looking at the Master Item for some information, such as this UPC code. It works differently than the PO specification designer, so OE Picking Slips has access to more information.