The general billing interface processes data that is formatted in table KOMFKGN (see Communication Structures ). If you want to consider user-defined data that exists in billing header table VBRK but not in table KOMFKGN, you proceed as follows:
Table KOMFKGN contains customer include KOMFKZZ. Enhance this structure with the corresponding VBRK field (e.g. value date VALDT).
Ensure data provision for the field (e.g.: KOMFKGN-VALDT).
The standard system document flow for billing of external transactions contains copying requirement 013 for billing type FX and sales document type TA Copy this requirement to a copying requirement within a customer name range (e.g.: 601). Enhance this new copying requirement with an ABAP statement that copies the newly defined field from internal table XKOMFGKN to table VBRK (e.g.: VBRK-VALDT = XKOMFKGN-VALDT).