Currently users can submit the PO to the workflow even if the PO exceeds the credit limit, its only after the workflow is approved then system stops the purchase order when user post product receipt.

From customer side, when submitting workflow to the Manager, the PO is being asked why the PO is exceeded credit limit but still user can submit it, which users want to prevent those kind of scenario. Secondly, when confirming the PO, the PO will be sent to Vendor and they will prepare goods to deliver. 

Hence, it should have the Vendor credit balance check for Purchase order when users confirm the Purchase orders.