Message type: E = Error
Message class:  FAGL_POSTING - Messages for FAGL_POSTING EhP3 Relating to New Functions 
Message number: 030
Message text: Changes to invoice reference not permitted
You are trying to change the invoice reference when document splitting
is activated.
However, doing so can lead to inconsistencies in the additional account
assignments in new General Ledger Accounting.
The required reassignment in General Ledger Accounting is not performed.
If you want to change invoice references, you need to repost the item
with the new invoice reference.
The system issues an error message and will not allow you to continue with this transaction until the error is resolved.
Error message extract from SAP system. Copyright SAP SE.
The SAP error message FAGL_POSTING030, which states "Changes to invoice reference not permitted," typically occurs during the posting of a financial document in the General Ledger (G/L) when there are attempts to modify the invoice reference of a document that has already been posted. This error is often related to the integrity of financial data and the need to maintain accurate records.
Cause: Document Status: The document you are trying to modify may already be posted, and SAP does not allow changes to certain fields, including the invoice reference, after posting. Document Type Restrictions: Certain document types may have restrictions on what can be changed after posting. Configuration Settings: The system configuration may restrict changes to specific fields in financial documents to ensure data integrity. User Authorizations: The user may not have the necessary authorizations to make changes to posted documents.
Solution: Check Document Status: Verify if the document is already posted. If it is, you cannot
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