Allocation number field in VOFA for IV billing type

Hi,

When I enter the accounting document number created by inter company billing document (IV) in table BSID then I am getting blank value in "Assignment" field. But in the BSIK table for Vendor there is a value in assignment field which is document number and year. For FI document clearing we are using a custom program which requires assignment field to be populated for both Vendor and Customer.

I checked in VOFA for IV billing type and the Allocation number field is blank whereas it is maintained as "F" (External delivery no. if avaialable, otherwise delivery no.) for both F1 and F2 billing type. Do I need to maintain F in Allocation number field for IV billing type also so that Assignment field gets populated in BSID?

Thanks,

Karan