DrCr/drcr/tax/aus_tax.py

#   DrCr: Web-based double-entry bookkeeping framework
#   Copyright (C) 2022–2023  Lee Yingtong Li (RunasSudo)
#
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU Affero General Public License as published by
#   the Free Software Foundation, either version 3 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU Affero General Public License for more details.
#
#   You should have received a copy of the GNU Affero General Public License
#   along with this program.  If not, see <https://www.gnu.org/licenses/>.

from ..config import TAX_MAPPING
from ..models import Amount, Posting, Transaction, TrialBalancer

from datetime import datetime

def taxable_income():
	balancer = TrialBalancer()
	balancer.apply_transactions(Transaction.query.all())
	
	result = Amount(0, '$')
	
	for account in TAX_MAPPING['Salary and wages']:
		result.quantity += int(balancer.accounts[account].quantity / 100) * 100
	for account in TAX_MAPPING['Government allowances']:
		result.quantity += int(balancer.accounts[account].quantity / 100) * 100
	for account in TAX_MAPPING['Work-related self-education expenses']:
		result.quantity += int(balancer.accounts[account].quantity / 100) * 100
	for account in TAX_MAPPING['Other work-related expenses']:
		result.quantity += int(balancer.accounts[account].quantity / 100) * 100
	
	return result

def base_income_tax(taxable_income):
	income = -taxable_income.as_cost().quantity
	
	if income <= 1820000:
		return Amount(0, '$')
	if income <= 4500000:
		return Amount(int((income - 1820000) * 0.19), '$')
	if income <= 12000000:
		return Amount(int(509200 + (income - 4500000) * 0.325), '$')
	if income <= 18000000:
		return Amount(int(2946700 + (income - 12000000) * 0.37), '$')
	return Amount(int(5166700 + (income - 18000000) * 0.45), '$')

def calculate_tax(taxable_income):
	income = -taxable_income.as_cost().quantity
	medicare_levy = int(income * 0.02)
	
	return Amount(base_income_tax(taxable_income).quantity + medicare_levy, '$')

def tax_transaction(taxable_income):
	tax = calculate_tax(taxable_income)
	
	# Get EOFY date
	dt = datetime.now().replace(month=6, day=30)
	if dt < datetime.now():
		dt = dt.replace(year=dt.year + 1)
	
	return Transaction(
		dt=dt,
		description='Estimated tax payable',
		postings=[
			Posting(account='Income Tax', quantity=tax.quantity, commodity='$'),
			Posting(account='Income Tax Control', quantity=-tax.quantity, commodity='$')
		]
	)