We have a requirement to process the payments received via Lockbox with reference to a Reference document number (XBLNR) first, if not found: Assignment number (ZUONR).
I have only below options in SAP.
1 Document numbers (BELNR)
2 Reference document numbers (XBLNR)
3 Document number first, if not found: reference doc. number
4 Reference document number first, if not found: doc. number
5 Document number first, then reference and amount
Please advise, if there is any SAP notes available or how to add new option to the above list.