Solution : https://service.sap.com/sap/support/notes/532052 (SAP Service marketplace login required)
Key words : 
document currencyabrbtr_off  bbrutto     13    2    curr   gross amountbrbtr      bbrutto     13    2    curr   gross amountwrbtr_tot  bnetto      13    2    curr   net amountwmwst_tot   wmwst      13    2    curr   tax amount, document currencybrbtr_rst  bbrutto     13    2    curr   gross amountoffwr      bnetto      13    2    curr   net amountwmwst_off   wmwst      13    2    curr   tax amount, type  lgth  dec  dtype  short text---------- -------- ----- --- ---- ----------------wmwst_rst   wmwst      13    2    curr   tax amount, type  lgth  dec  dtype  short text---------- -------- ----- --- ---- -----------------rstwr      bnetto      13    2    curr   net amount 3, document currencybrbtr_tot  bbrutto     13    2    curr  gross amountthe reference field, payment amount        i_gesanz = 'x'     --> entire, reference field    ssdaccdpc  waers, billing document printout, includes gross amount, net amount
Related Notes : 
       
| 652786 | SAPscript: Down payment information is generally printed | 
| 638658 | SAPscript down payment print: VAT in final amount | 
| 626451 | SAPscript: Invoice printout with down payments | 
| 570450 | SmartForms: Down payments in billing document printout (4) | 
| 569318 | Enhancement of billing document printout: Down payments (4) | 
| 555279 | Enhancement of billing document printout: Down payments (3) | 
| 555273 | Smart Forms: Down payments in billing doc print (3) | 
| 537916 | Smart Forms: Down payments in billing doc print (2) | 
| 523803 | Enhancement of billing doc print: Down payments (2) | 
| 429677 | SmartForms: Down payments in billing doc print (1) | 
| 304408 | Enhancement of billing document printout: Down payments (1) | 
| 113347 | Down payment process. as of Release 4.0x (standard) |