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

SAP Error Message - Details

• 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.

Smart SAP Assistant

• What is the cause and solution for SAP error message FKKINV018 - External tax item number &3 is not unique ?

  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 transaction codes like SE16 or SE11 to query the relevant database tables (e.g., TFKTAX) to identify where the duplicate external tax item numbers exist.
  Correct Duplicates: Once identified, you can either:
  
  Modify the existing entries to ensure that each external tax item number is unique.
  Delete or archive unnecessary duplicates if they are not needed.
  
  
  Review Configuration: Check the configuration settings for tax codes and ensure that they are set up correctly to prevent duplicates from being created in the future.
  Data Validation: Implement data validation checks during data entry or migration processes to catch duplicates before they are saved in the system.
  Consult Documentation: Review SAP documentation or consult with your SAP support team for specific guidelines related to your version of SAP and the tax configuration.
  
  Related Information:
  
  Transaction Codes: Familiarize yourself with relevant transaction codes such as FBL1N (Vendor Line Item Display), FBL3N (G/L Account Line Item Display), and FBL5N (Customer Line Item Display) to analyze related financial documents.
  SAP Notes: Check SAP Notes for any known issues or patches related to this error message. SAP Notes can provide additional context or solutions that are specific to your version of SAP.
  Testing: After making changes, conduct thorough testing to ensure that the issue is resolved and that no new issues have been introduced.
  
  If the problem persists after following these steps, it may be beneficial to engage with SAP support or a consultant who specializes in SAP Financials for further assistance.