How To Fix FKKINV018 - External tax item number &3 is not unique

FKKINV018 - Overview

• Message type: E = Error

• Message class: FKKINV - Invoicing in Contract Accounts Receivable and Payable

• Message number: 018

• Message text: External tax item number &3 is not unique

What causes this issue?

In a billing document with <DS:DE.REFDOCNO_KK>external document number
</> &v1& in <DS:DE.LOGSYS>logical system</> &v2&, the
<DS:DE.REFTAXITEM_KK>tax item number in external system</> &v3& is not
unique.

System Response

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

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.

FKKINV018 - Details

• The SAP error message FKKINV018 indicates that there is a problem with the external tax item number in the context of invoicing or billing within the SAP system. Specifically, the message states that the external tax item number is not unique, which means that the system has found multiple entries with the same external tax item number, leading to ambiguity.
  
  Cause:
  
  Duplicate External Tax Item Numbers: The most common cause of this error is that the same external tax item number has been assigned to multiple tax items in the system. This can happen due to data entry errors, incorrect configuration, or issues during data migration.
  
  Configuration Issues: There may be issues in the configuration of tax codes or tax items that lead to non-unique identifiers being generated or assigned.
  Data Migration Issues: If data has been migrated from another system, it is possible that duplicate external tax item numbers were imported.
  
  
  Solution:
  
  Identify Duplicates: Use