Type of message:  This is an internal message for MediusGo. 

Cause: An invoice with the same invoice number from the same vendor already exists in the current company.

Action: Check that both invoices should exist and, if so, change the invoice number on one of the invoices.

What counts as duplicate invoices is set in the Administration tool - Invoice - Invoice duplicate.

If none of this solves the problem, contact the MediusGo Customer Center via the support button on the invoice or our Customer portal.