BU derivation

Summary:

I'm aware of the possible flows,

• Blank
• Email Routing Attribute
• Sender's Email Address
• Recipient Email Address

only "Blank" works for us due to the complexity of our supplier relationships (multiple instances across BUs).

My question is this:

When an incorrect BU is derived because the purchase order has not been found how do you re-train IDR? The invoice keeps coming in to IDR as "Needs revalidation" at this point i cannot remove the lines or adjust the BU as it's fixed and there is no way of retrospectively adding the PO number. My only option is to delete the entry and manually key the invoice but then IDR isn't learning and i continue in this cycle of not being able to intervene in the process and recognise the PO.