Explanation
When you post an invoice with invoice reduction, two accounting documents are created: one for the invoice posting and one for the credit memo posting. A message is also created that can be issued to the supplier as a notification of a credit memo posting. The invoice is not blocked for payment until the supplier confirms the credit memo receipt, and only one accounting document is not created, containing both the invoice and the credit memo postings. References: [SAP Help Portal - Invoice Reduction]