From dca300fd580864ac4b8df17923f55f19fdc50c5a Mon Sep 17 00:00:00 2001
From: RunasSudo <runassudo@yingtongli.me>
Date: Fri, 16 Aug 2024 22:20:45 +1000
Subject: [PATCH] austax: Add Medicare levy surcharge

---
 austax/reports.py    | 34 +++++++++++++++++++++++++++++-----
 austax/tax_tables.py | 13 +++++++++++++
 2 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/austax/reports.py b/austax/reports.py
index b7051eb..79352c0 100644
--- a/austax/reports.py
+++ b/austax/reports.py
@@ -20,7 +20,7 @@ from drcr.models import AccountConfiguration, Amount, Metadata, Transaction, Tri
 from drcr.reports import Calculated, Report, Section, Spacer, Subtotal, entries_for_kind
 from drcr.webapp import eofy_date, sofy_date
 
-from .tax_tables import base_tax, medicare_levy_threshold, repayment_rates, fbt_grossup
+from .tax_tables import base_tax, medicare_levy_threshold, medicare_levy_surcharge_single, repayment_rates, fbt_grossup
 
 def base_income_tax(year, taxable_income):
 	"""Get the amount of base income tax"""
@@ -59,6 +59,13 @@ def medicare_levy(year, taxable_income):
 	# Normal Medicare levy
 	return Amount(int(taxable_income.quantity * 0.02), '$')
 
+def medicare_levy_surcharge(year, taxable_income, rfb_grossedup):
+	mls_income = taxable_income + rfb_grossedup
+	
+	for i, (upper_limit, rate) in enumerate(medicare_levy_surcharge_single[year]):
+		if upper_limit is None or mls_income.quantity <= upper_limit * (10**AMOUNT_DPS):
+			return Amount(rate * mls_income.quantity, '$')
+
 def study_loan_repayment(year, taxable_income, rfb_grossedup):
 	"""Get the amount of mandatory study loan repayment"""
 	
@@ -165,6 +172,21 @@ def tax_summary_report():
 					bordered=True
 				),
 				Spacer(),
+				Section(
+					entries=[
+						Calculated(
+							'Taxable value of reportable fringe benefits',
+							lambda _: -sum((e.amount for e in entries_for_kind(account_configurations, accounts, 'austax.rfb')), Amount(0, '$')),
+							id='rfb_taxable'
+						),
+						Calculated(
+							'Grossed-up value',
+							lambda _: Amount(report.by_id('rfb_taxable').amount.quantity * fbt_grossup[eofy_date().year], '$'),
+							id='rfb_grossedup'
+						)
+					],
+					visible=False  # Precompute RFB amount as this is required for MLS
+				),
 				Section(
 					entries=[
 						Calculated(
@@ -175,6 +197,10 @@ def tax_summary_report():
 							'Medicare levy',
 							lambda _: medicare_levy(eofy_date().year, report.by_id('taxable').amount)
 						),
+						Calculated(
+							'Medicare levy surcharge',
+							lambda _: medicare_levy_surcharge(eofy_date().year, report.by_id('taxable').amount, report.by_id('rfb_grossedup').amount)
+						),
 						Subtotal('Total income tax', id='total_tax', bordered=True)
 					]
 				),
@@ -191,13 +217,11 @@ def tax_summary_report():
 					entries=[
 						Calculated(
 							'Taxable value of reportable fringe benefits',
-							lambda _: -sum((e.amount for e in entries_for_kind(account_configurations, accounts, 'austax.rfb')), Amount(0, '$')),
-							id='rfb_taxable'
+							lambda _: report.by_id('rfb_taxable').amount
 						),
 						Calculated(
 							'Grossed-up value',
-							lambda _: Amount(report.by_id('rfb_taxable').amount.quantity * fbt_grossup[eofy_date().year], '$'),
-							id='rfb_grossedup'
+							lambda _: report.by_id('rfb_grossedup').amount
 						),
 						Calculated(
 							'Mandatory study loan repayment',
diff --git a/austax/tax_tables.py b/austax/tax_tables.py
index 83c6a00..2bc6b33 100644
--- a/austax/tax_tables.py
+++ b/austax/tax_tables.py
@@ -91,6 +91,19 @@ medicare_levy_threshold = {
 	2022: (23365, 29207)
 }
 
+# Medicare levy surcharge rates (singles)
+# https://www.ato.gov.au/individuals-and-families/medicare-and-private-health-insurance/medicare-levy-surcharge/medicare-levy-surcharge-income-thresholds-and-rates
+# Maps each financial year to list of (upper limit (INclusive), MLS rate)
+# FIXME: Only supports singles
+medicare_levy_surcharge_single = {
+	2024: [
+		(93000, 0),
+		(108000, 0.01),
+		(144000, 0.0125),
+		(None, 0.015)
+	]
+}
+
 # FBT type 1 gross-up factor
 # https://www.ato.gov.au/rates/fbt/#GrossupratesforFBT
 fbt_grossup = {