Solution : https://service.sap.com/sap/support/notes/306529 (SAP Service marketplace login required)
Summary : 
      When posting an invoice to a one-time account for an Australian company, the VAT registration number field (STCEG) is not input-ready. This issue, found under transactions like FB01 and involving Australian Business Numbers, results from a program error. SAP recommends implementing the attached corrections to resolve this flaw.
Key words : 
field vat registration rumber, additional key words fb01, australian company code, australian business number, -time account, program error, solution implement, attached corrections, prerequisites
Related Notes : 
       
| 216761 | RFUVDE00: Termination with error message F7 212 | 
| 216359 | Australian GST: Simplified BAS reporting | 
| 216109 | GST - Simplified ERS reporting | 
| 215964 | FB01/FB70: Cash discount base amount not set | 
| 212933 | Error F2013 'Country &1 not defined in system' | 
| 211354 | Rounding withholding Taxes in Australia | 
| 208810 | RFUVDE00: rounding of base amounts not required | 
| 204972 | RFUMSV00: Deactivating document summarization (BSET) | 
| 203365 | BAS - Report for processing the GST in Australia | 
| 202730 | ERS processing for GST tax Australia | 
| 201753 | ABN: Australian business number | 
| 168188 | GST Information Note | 
| 122332 | RFUMSV00 Wrong transaction key for n.ded.input tax | 
| 73699 | VAT registration number check in Greece and Finland |