Hi Shilpa Sunil,
in your original post you had two questions, how to populate VKBUR on item and how on header level in the invoice.
I replied to both.
On invoice header (VBRK) a field VKBUR is not existing, therefore if you really want to have it, then a modification of table VBRK would be necessary, with additional user-exit programming to fill the new Z field.
This extension would not affect the FI document, since there in standard a corresponding field does not exist for VKBUR in the FI tables (check table BSEG).
It would also not be printed automatically, since the print-out depends on your defined FORM and custom own printing program, where you first would have to add logic to make printing possible.
If you create this header field in VBRK you have to be aware that it could lead to invoice splits, if VKBUR is filled differently.
However the question remains, if you need the field for reporting purposes only, why don't you take the information from the item level, where the field VBRP-VKBUR is present in standard?
Best regards,
Tobias