taxes.rb

def estimated_tax
  line1   = expected_agi
  line2   = deductions
  line3   = line1 - line2
  line4   = 3700 * exemptions
  line5   = line3 - line4
  line6   = tax(line5)
  line7   = alt_min_tax
  line8   = line6 + line7
  line9   = credits
  line10  = max(0, line8 - line9)
  line12  = other_taxes
  line13a = line10 + line11 + line12
  line13b = 0 # Misc credits
  line13c = max(0, line13a - line13b)
  line14a = line13c * (farmer || fisherman ? 2/3 : 0.9)
  line14b = 0 # Required annual payment based on prior year's tax
  line14c = min(line14a, line14b)
  line15  = 0 # Income tax withheld and estimated to be withheld
  line16a = line14c - line15
  line16b = line13c - line15
  line17  = line16a / 4 - overpayment

  if line16a <= 0 || line16b < 1000
    return 0
  end

  return line17
end