Fields BSEG-VBEL2 and BSEG-POSN2 are not being transferred to FI document

Hi Gurus,

When we transfer a billing document to FI Accounting using transaction VF02, fields BSEG-VBEL2 and BSEG-POSN2 are not being transferred to FI GL document. Nevertheless both fields are filled in billing document.

What must i do to transfer these two fields to FI GL document?

Best Regards