Manual invoice inter-company purchase orders

Adding to the previous posts regarding the setup you require, ensure you have the below setup on the customer master card (which you probably have already since orders are being created in legal entities)

if your process dictates processing the respective documents (PO receipt and invoice) from the sales order you need to perform the folloing:

1. Once you post the packing slip from the sales order--> open the packing slip journal--> post the intercompany packing slip 

Result: PO receipt posted automatically

2. Post the invoice from the sales order and then go to invoice journal-->Intercompany invoice posting 

Result: PO invoice posted

Hope this helps.