Transfer the additional custom field values from sales order to billing document using data transfer routine
Steps :
Go to the transaction VOFM
Select Data Transfer from the Menu and select Billing documents
Create a new routine ex: 901
Code inside the routine:
vbrp-zz1_stock_custom_bdi = vbap-zz1_stock_custom_sdi.
vbrp-zz1_sales_type_bdi = vbap-zz1_sales_type_sdi.
