PPH21's one year formula system

PPH21 one year formula at Indonesia system

Variables
A = current month salary + total previuos month salary + THR (if there is)
B = total previous month of PPH + THR's PPH (if there is)
C = maximal expense position (Maksimal Biaya Jabatan) (1.296.000)
H = expense position (Biaya jabatan) (5%)
I = PPH21 (5%)

Formula
D = (A / current month) * 12 (according to year of working)
E = D * H
if E > C then E = C

F = D - (E + PTKP one year)

G = ((F * I) / 12) * current month

tax of current month = ( G - B )