S S = BRUTE X 9%
IRG = BRUTE - SS X 10%
NET = BRUTE - SS - IRG
EXEMPLE
SB 15000.00
IEP 6250.00
NOTE 30
15000.00+6250.00X30/100 = 6375.00
6375.00X3= 19125.00
19125.00x9/100=1721.25
19125.00-1721.25=17403.75
17403.75x10/100=1740.37
19125.00-1751.25-1740.37=15633.38