Я использовал customer-exit EXIT_SAPLV60B_008
Этот exit вызывается в ФМ RV_ACCOUNTING_DOCUMENT_CREATE при создании бухгалтерского документа по фактуре.

EXIT_SAPLV60B_001: Change the header data in the structure acchd
You can use this exit to influence the header information of the accounting document. For example, you can change the business transaction, "created on" date and time, the name of the person who created it or the transaction with which the document was created.
EXIT_SAPLV60B_002: Change the customer line ACCIT
You can use this exit to change the customer line in the accounting document. This exit is processed once the ACCIT structure is filled in with data from document header VBRK.
EXIT_SAPLV60B_003: Change the customer line in costing
The customer line is filled in differently for costing. You can use exit 003 to influence the ACCIT structure.
EXIT_SAPLV60B_004: Change a GL account item ACCIT You can add information to a GL account item (such as quantity specifications) with this exit.
EXIT_SAPLV60B_005: User exit for accruals
Once all relevant data for accruals was entered in the GL account item, you can add to this data with this exit.
EXIT_SAPLV60B_006: Change the control line ACCIT
You can use exit 006 to add information to the control line.
EXIT_SAPLV60B_007: Change the installment plan
You can use exit 007 to add information to the installment plan
parameters in the GL account item.
EXIT_SAPLV60B_008: Change the transfer structure ACCCR, ACCIT and ACCHD
After the accounting document is filled in with data, you can use exit 008 to change the document once again.
EXIT_SAPLV60B_010: Item table for customer lines
You can use exit 10 to influence the contents of customer lines before they are created.
EXIT_SAPLV60B_0011: Change the parameter for cash account determination or reconciliation account determination
You can use this exit to change inbound parameters in order to influence account determination.