Solution : https://service.sap.com/sap/support/notes/440567 (SAP Service marketplace login required)
Key words :
awtyp awref kposn mwskz shpto pos_no accnt_nobkpf 1234567890 002999 u1 223334444 00002 1234567890bkpf 1234567890 999999 u1 000000 <<<< incorrect, update flag ttxi-uflag, withholding tax code calculates, terms classic withholding tax, withholding tax base amount, classic withholding tax, base amount net, attached source code, net base reason, external tax system
Related Notes :
| 444251 | Double entries in TTXY in case of withholding tax net |