Script to apply taxes to an amount. Updated for 2021 tax year rates.

taxcalc.py

@@ -0,0 +1,93 @@
+#!/usr/bin/python3
+''' Calculate SARS tax on payments '''
+
+import locale
+import math
+import re
+import sys
+
+tax_rates = [
+    dict(
+        rate = 18,
+        low = 1,
+    ), dict(
+        rate = 26,
+        low = 205_901,
+    ), dict(
+        rate = 31,
+        low = 321_601,
+    ), dict(
+        rate = 36,
+        low = 445_101,
+    ), dict(
+        rate = 39,
+        low = 584_201,
+    ), dict(
+        rate = 41,
+        low = 744_801,
+    ), dict(
+        rate = 45,
+        low = 1_577_301,
+    ),
+]
+for r in tax_rates:
+    idx = tax_rates.index(r)
+    if idx < len(tax_rates) - 1:
+        high = tax_rates[idx+1].get('low')
+        r['high'] = high - 1
+    else:
+        r['high'] = False
+
+def error(e):
+    if e:
+        print(e);
+    print("{0}: Please enter the annual or monthly amount before tax".format(sys.argv[0]))
+    sys.exit()
+
+locale.setlocale( locale.LC_MONETARY, 'en_ZA.UTF-8' )
+locale._override_localeconv = {'mon_thousands_sep': ' ', 'mon_decimal_point': ','}
+currency = locale.localeconv()
+
+if len(sys.argv) < 2:
+    error()
+elif isinstance(sys.argv[1], str):
+    try:
+        amount = "".join(sys.argv[1:]).strip(currency.get('currency_symbol'))
+        amount = re.sub('[,.](\d{2})$','.\g<1>', amount) # convert decimal separator to .
+        amount = re.sub('[ ,](\d{3})','\g<1>', amount)   # convert thousands separator to ''
+        amount = locale.atof(amount)
+        amount = int(amount)
+    except Exception as e:
+        error(e)
+else: 
+    error()
+
+''' Are we dealing with a monthly amount or annual amount? 
+    Assume anything over R100k is annual.
+    If earning more than 100k per month, convert to --month/--year commandline option
+'''
+if amount > 100_000:
+    is_annual = True
+else:
+    is_annual = False
+    print("Notice: value {} determined to be per month, dividing tax rates by 12".format(amount))
+
+total_tax = 0
+for r in tax_rates:
+    low = (r.get('low') - 1)
+    high = r.get('high')
+    rate = r.get('rate')
+    if not is_annual:
+        low = math.ceil(low/12)
+        high = math.ceil(high/12)
+    if amount >= low:
+        bracket = amount
+        if high and amount > high:
+            bracket = high
+        current = math.ceil(bracket - low)
+        total_tax += math.ceil(current * rate / 100)
+        print("  {:>6} - {:>6} = {:>6} / {} = {:>6}".format(bracket, low, current, rate, total_tax))
+        if amount < high:
+            break
+
+print("\nTotal tax on {} is {}".format(locale.currency(amount, grouping=True), locale.currency(total_tax, grouping=True)))