During create the following may be usueful: 
SDVFX001 

User exit header line in delivery to accounting 
SDVFX002 

User exit for A/R line in transfer to accounting 
SDVFX003 

User exit cash clearing in transfer to accounting 
SDVFX004 

User exit G/L line in transfer to accounting 
SDVFX005 

User exit reserves in transfer to accounting 
SDVFX006 

User exit tax line in transfer to accounting 
SDVFX007 

User exit: Billing plan during transfer to Accounting 
SDVFX008 

User exit: Processing of transfer structures SD-FI 
SDVFX009 

Billing doc. processing KIDONO (payment reference number) 
SDVFX010 

User exit item table for the customer lines 
SDVFX011 

Userexit for the komkcv- and kompcv-structures 
V05I0001 

User exits for billing index 
V05N0001 

User Exits for Printing Billing Docs. using POR Procedure 
V60A0001 

Customer functions in the billing document 
V60P0001 

Data provision for additional fields for display in lists 
V61A0001 

Customer enhancement: Pricing 
J_3RSINV 
Serkan AKKAVAK
Computer Engineer
ABAP Developer & SAP MM SD Consultant
Contact : serkurumsal@yandex.com