How To Fix FKKBIX2011 - Item for source trans. &1 is a duplicate according to check schema &2

FKKBIX2011 - Overview

• Message type: E = Error

• Message class: FKKBIX2 - Billing in Contract Accounts Receivable and Payable

• Message number: 011

• Message text: Item for source trans. &1 is a duplicate according to check schema &2

What causes this issue?

For the item being transferred of business partner &v3& with source
transaction &v1&, an unreversed <DS:TX.FKKBIX_BIT>billable item</>
already exists, which, according to the <DS:DE.BIT_DCFIELD_KK>comparison
fields</> entered in <DS:DE.BIT_DCSCHEMA_KK>check schema</> &v2& for the
duplicate check, is identical with the item being transferred.
The item was transferred nonetheless, since the item was released for
billing (see <DS:DE.BIT_DUPREC_KK>Billable Item Was Loaded Twice</>).

System Response

The billable item was transferred.

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.

FKKBIX2011 - Details

• The SAP error message FKKBIX2011 indicates that there is a duplicate item in the context of a source transaction, which is being checked against a specified check schema. This error typically arises during the processing of financial documents, particularly in the context of invoice verification or payment processing.
  
  Cause:
  The error occurs when the system detects that an item being processed is a duplicate of another item based on the criteria defined in the check schema. This can happen due to several reasons:
  
  Duplicate Entries: The same item has been entered multiple times in the transaction.
  Incorrect Data Entry: Data might have been entered incorrectly, leading to the system interpreting it as a duplicate.
  
  Configuration Issues: The check schema might be configured in a way that is too strict, causing legitimate entries to be flagged as duplicates.
  Data Migration Issues: If data has been migrated from another system, duplicates may have been inadvertently created.
  
  
  Solution:
  To resolve the