Invoice created in SUS vs created in ECC

Hi Gurus,

I think I know the answer to this one, but I'm going to ask anyway...

If we have a PO & GR for 100 units, and a supplier mails/email/faxes an invoice to AP for 10 units, and a MIRO invoice is created, and then they create an invoice in SUS for 100 units, the SUS invoice will error out when the IDoc is created in ECC. Is there any way for this to create some kind of notification? The supplier made a mistake in this case, but unless someone is monitoring IDocs, how would anyone know that this happened?

I'm guessing this would have to be a custom solution, but is that how others have addressed the issue of inbound Idocs that fail?

Thanks,
Seth