'Standardized document' was changed by document splitting.

What causes this issue?

You post a document that is only updated in the universal journal (table
ACDOCA) and does not have an entry view of the BSEG table.
The system displays this error message because this document was changed
by document splitting in Financial Accounting (account assignments were
added, lines were split). Funds Management requires a document with an
entry view to ensure that the update is performed correctly.

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?

If this document was generated by a standard SAP process, check whether
this document can be posted with an entry view (see SAP Note 2670040 for
foreign currency valuation).
If this is not possible (such for depreciation postings in Asset
Accounting), assign the corresponding document type to a suitable b
usiness transaction variant, which does not change the document.
If the posting comes from a customer-specific program or is generated
using an interface, post the document with an entry view of the table
BSEG, or post it with a complete account assignment so that document
splitting is no longer required.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.