How To Fix VFKK120 - Billing type of reversal &1 or original &2 not of type billing request

VFKK120 - Overview

• Message type: E = Error

• Message class: VFKK -

• Message number: 120

• Message text: Billing type of reversal &1 or original &2 not of type billing request

What causes this issue?

The <DS:DE.FKART>billing type</> &V2& and the assigned reversal billing
type &V1& both have to be from the <DS:DE.FKTYP>billing category</> <LS>
billing request</> (U).

Error message extract from SAP system. Copyright SAP SE.

VFKK120 - Details

• The SAP error message VFKK120 indicates that there is an issue with the billing types involved in a reversal or original billing document. Specifically, it suggests that the billing type of the reversal document (denoted as &1) or the original document (denoted as &2) is not of the type "billing request." This can occur in scenarios where you are trying to reverse a billing document that does not meet the necessary criteria for reversal.
  
  Cause:
  
  Incorrect Billing Type: The original billing document or the reversal document is not of the expected billing type. For example, if the original document is a credit memo or an invoice, and you are trying to reverse it with a billing request type, this error will occur.
  
  Configuration Issues: The billing types may not be configured correctly in the system, leading to mismatches in expected document types.
  Document Status: The original document may be in a status that does