austax: Port full income tax implementation from Python
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@ -20,6 +20,7 @@ local tax_tables = require('../austax/tax_tables')
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local calc = {}
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-- Get the amount of base income tax
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function calc.base_income_tax(net_taxable: number, context: libdrcr.ReportingContext): number
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local year, _, _ = libdrcr.parse_date(context.eofy_date)
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local base_tax_table = tax_tables.base_tax[year]
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@ -36,11 +37,93 @@ function calc.base_income_tax(net_taxable: number, context: libdrcr.ReportingCon
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end
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if net_taxable <= upper_limit then
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return flat_amount + marginal_rate * (net_taxable - lower_limit)
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return flat_amount + math.floor(marginal_rate * (net_taxable - lower_limit))
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end
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end
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error('Taxable income not within any tax bracket')
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end
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-- Get the amount of low income tax offset
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-- https://www.ato.gov.au/forms-and-instructions/low-and-middle-income-earner-tax-offsets
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/itaa1997240/s61.115.html
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function calc.lito(net_taxable: number, tax_total: number, context: libdrcr.ReportingContext): number
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if net_taxable <= 37500 * (10 ^ context.dps) then
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-- LITO is non-refundable
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-- FIXME: This will not work if we implement multiple non-refundable tax offsets
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if tax_total <= 700 * (10 ^ context.dps) then
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return tax_total
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else
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return 700 * (10 ^ context.dps)
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end
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elseif net_taxable <= 45000 * (10 ^ context.dps) then
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return 700 * (10 ^ context.dps) - math.floor(0.05 * (net_taxable - 37500 * (10 ^ context.dps)))
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elseif net_taxable <= 66667 * (10 ^ context.dps) then
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return 325 * (10 ^ context.dps) - math.floor(0.015 * (net_taxable - 45000 * (10 ^ context.dps)))
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else
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return 0
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end
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end
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-- Get the amount of Medicare levy
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function calc.medicare_levy(net_taxable: number, context: libdrcr.ReportingContext): number
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local year, _, _ = libdrcr.parse_date(context.eofy_date)
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local threshold_table = tax_tables.medicare_levy_threshold[year]
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local lower_threshold = threshold_table[1] * (10 ^ context.dps)
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local upper_threshold = threshold_table[2] * (10 ^ context.dps)
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if net_taxable < lower_threshold then
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return 0
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elseif net_taxable < upper_threshold then
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-- Medicare levy is 10% of the amount above the lower threshold
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return math.floor((net_taxable - lower_threshold) * 0.1)
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else
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-- Normal Medicare levy
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return math.floor(net_taxable * 0.02)
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end
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end
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-- Get the amount of Medicare levy surcharge
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function calc.medicare_levy_surcharge(net_taxable: number, rfb_grossedup: number, context: libdrcr.ReportingContext): number
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local mls_income = net_taxable + rfb_grossedup
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local year, _, _ = libdrcr.parse_date(context.eofy_date)
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local mls_table = tax_tables.medicare_levy_surcharge_single[year]
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for _, row in ipairs(mls_table) do
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local upper_limit = row[1] * (10 ^ context.dps)
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local rate = row[2]
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if mls_income <= upper_limit then
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return math.floor(rate * mls_income)
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end
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end
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error('MLS income not within any MLS bracket')
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end
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-- Calculate the grossed-up reportable fringe benefit
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function calc.rfb_grossup(rfb_taxable: number, context: libdrcr.ReportingContext): number
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return math.floor(rfb_taxable * tax_tables.fbt_grossup)
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end
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-- Get the amount of mandatory study loan repayment
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function calc.study_loan_repayment(net_taxable: number, rfb_grossedup: number, context: libdrcr.ReportingContext): number
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local repayment_income = net_taxable + rfb_grossedup
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local year, _, _ = libdrcr.parse_date(context.eofy_date)
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local repayment_table = tax_tables.study_loan_repayment_rates[year]
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for _, row in ipairs(repayment_table) do
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local upper_limit = row[1] * (10 ^ context.dps)
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local rate = row[2]
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if repayment_income < upper_limit then
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return math.floor(rate * repayment_income)
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end
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end
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error('HELP repayment income not within any repayment bracket')
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end
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return calc
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@ -111,7 +111,7 @@ function reporting.CalculateIncomeTax.execute(args, context, kinds_for_account,
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visible = true,
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link = nil,
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heading = true,
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bordered = true,
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bordered = false,
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}})
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table.insert(report.entries, { Section = section })
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table.insert(report.entries, 'Spacer')
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@ -159,7 +159,7 @@ function reporting.CalculateIncomeTax.execute(args, context, kinds_for_account,
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visible = true,
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link = nil,
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heading = true,
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bordered = true,
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bordered = false,
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}})
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table.insert(report.entries, { Section = section })
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table.insert(report.entries, 'Spacer')
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@ -202,8 +202,45 @@ function reporting.CalculateIncomeTax.execute(args, context, kinds_for_account,
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bordered = false,
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}})
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-- Medicare levy row
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local tax_ml = calc.medicare_levy(net_taxable, context)
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if tax_ml ~= 0 then
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table.insert(report.entries, { Row = {
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text = 'Medicare levy',
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quantity = {tax_ml},
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id = 'tax_ml',
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visible = true,
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link = nil,
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heading = false,
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bordered = false,
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}})
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end
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-- Precompute RFB amount as this is required for MLS
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local rfb_taxable = 0
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for account, kinds in pairs(kinds_for_account) do
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if libdrcr.arr_contains(kinds, 'austax.rfb') then
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rfb_taxable -= balances[account] or 0 -- Invert as income = credit balances
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end
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end
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local rfb_grossedup = calc.rfb_grossup(rfb_taxable, context)
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-- Medicare levy surcharge row
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local tax_mls = calc.medicare_levy_surcharge(net_taxable, rfb_grossedup, context)
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if tax_mls ~= 0 then
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table.insert(report.entries, { Row = {
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text = 'Medicare levy surcharge',
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quantity = {tax_mls},
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id = 'tax_mls',
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visible = true,
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link = nil,
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heading = false,
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bordered = false,
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}})
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end
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-- Total income tax row
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local tax_total = tax_base
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local tax_total = tax_base + tax_ml + tax_mls
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table.insert(report.entries, { Row = {
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text = 'Total income tax',
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quantity = {tax_total},
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@ -213,10 +250,126 @@ function reporting.CalculateIncomeTax.execute(args, context, kinds_for_account,
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heading = true,
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bordered = true,
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}})
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table.insert(report.entries, 'Spacer')
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-- Generate income tax transaction
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-- Low income tax offset row
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local offset_lito = calc.lito(net_taxable, tax_total, context)
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if offset_lito ~= 0 then
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table.insert(report.entries, { Row = {
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text = 'Low income tax offset',
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quantity = {offset_lito},
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id = nil,
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visible = true,
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link = nil,
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heading = false,
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bordered = false,
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}})
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end
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-- Total tax offsets row
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local offset_total = offset_lito
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if offset_total ~= 0 then
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table.insert(report.entries, { Row = {
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text = 'Total tax offsets',
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quantity = {offset_total},
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id = nil,
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visible = true,
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link = nil,
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heading = true,
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bordered = false,
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}})
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table.insert(report.entries, 'Spacer')
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end
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-- Calculate mandatory study loan repayment
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local study_loan_repayment = calc.study_loan_repayment(net_taxable, rfb_grossedup, context)
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-- Mandatory study loan repayment section
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if study_loan_repayment ~= 0 then
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-- Taxable value of reportable fringe benefits row
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if rfb_taxable ~= 0 then
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table.insert(report.entries, { Row = {
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text = 'Taxable value of reportable fringe benefits',
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quantity = {rfb_taxable},
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id = 'rfb_taxable',
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visible = true,
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link = nil,
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heading = false,
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bordered = false,
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}})
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end
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-- Grossed-up value row
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if rfb_grossedup ~= 0 then
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table.insert(report.entries, { Row = {
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text = 'Grossed-up value',
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quantity = {rfb_grossedup},
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id = 'rfb_grossedup',
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visible = true,
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link = nil,
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heading = false,
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bordered = false,
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}})
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end
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-- Mandatory study loan repayment row
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table.insert(report.entries, { Row = {
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text = 'Mandatory study loan repayment',
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quantity = {study_loan_repayment},
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id = 'study_loan_repayment',
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visible = true,
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link = nil,
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heading = true,
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bordered = false,
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}})
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table.insert(report.entries, 'Spacer')
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end
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-- Add PAYGW entries
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local total_paygw = 0
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local entries = entries_for_kind('austax.paygw', false, balances, kinds_for_account)
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if #entries ~= 0 then
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local section: libdrcr.Section = {
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text = 'PAYG withheld amounts',
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id = nil,
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visible = true,
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entries = entries,
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}
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table.insert(report.entries, { Section = section })
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total_paygw = math.floor(entries_subtotal(entries) / 100) * 100
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end
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-- Total PAYGW row
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if total_paygw ~= 0 then
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table.insert(report.entries, { Row = {
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text = 'Total withheld amounts',
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quantity = {total_paygw},
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id = 'total_paygw',
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visible = true,
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link = nil,
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heading = true,
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bordered = false,
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}})
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table.insert(report.entries, 'Spacer')
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end
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-- ATO liability row
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local ato_payable = tax_total - offset_total - total_paygw + study_loan_repayment
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table.insert(report.entries, { Row = {
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text = 'ATO liability payable (refundable)',
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quantity = {ato_payable},
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id = 'ato_payable',
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visible = true,
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link = nil,
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heading = true,
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bordered = true,
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}})
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-- Generate income tax transactions
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local transactions: {libdrcr.Transaction} = {
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{
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-- # Estimated tax payable
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id = nil,
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dt = libdrcr.date_to_dt(context.eofy_date),
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description = 'Estimated income tax',
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@ -226,23 +379,83 @@ function reporting.CalculateIncomeTax.execute(args, context, kinds_for_account,
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transaction_id = nil,
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description = nil,
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account = 'Income Tax',
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quantity = tax_total,
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quantity = (tax_total - offset_total),
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commodity = context.reporting_commodity,
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quantity_ascost = tax_total,
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quantity_ascost = (tax_total - offset_total),
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},
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{
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id = nil,
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transaction_id = nil,
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description = nil,
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account = 'Income Tax Control',
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quantity = -tax_total,
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quantity = -(tax_total - offset_total),
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commodity = context.reporting_commodity,
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quantity_ascost = -tax_total,
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}
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quantity_ascost = -(tax_total - offset_total),
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},
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},
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},
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{
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-- Mandatory study loan repayment
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id = nil,
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dt = libdrcr.date_to_dt(context.eofy_date),
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description = 'Mandatory study loan repayment payable',
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postings = {
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{
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id = nil,
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transaction_id = nil,
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description = nil,
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account = 'HELP',
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quantity = study_loan_repayment,
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commodity = context.reporting_commodity,
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quantity_ascost = study_loan_repayment,
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},
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{
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id = nil,
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transaction_id = nil,
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description = nil,
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account = 'Income Tax Control',
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quantity = -study_loan_repayment,
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commodity = context.reporting_commodity,
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quantity_ascost = -study_loan_repayment,
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},
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},
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}
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}
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-- Transfer PAYGW balances to Income Tax Control
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for account, kinds in pairs(kinds_for_account) do
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if libdrcr.arr_contains(kinds, 'austax.paygw') then
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local balance = balances[account] or 0
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if balance ~= 0 then
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table.insert(transactions, {
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id = nil,
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dt = libdrcr.date_to_dt(context.eofy_date),
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description = 'PAYG withheld amounts',
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postings = {
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{
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id = nil,
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transaction_id = nil,
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description = nil,
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account = 'Income Tax Control',
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quantity = balance,
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commodity = context.reporting_commodity,
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quantity_ascost = balance,
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},
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{
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id = nil,
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transaction_id = nil,
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description = nil,
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account = account,
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quantity = -balance,
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commodity = context.reporting_commodity,
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quantity_ascost = -balance,
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},
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},
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})
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end
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end
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end
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return {
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[{ name = 'CalculateIncomeTax', kind = 'Transactions', args = 'VoidArgs' }] = {
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Transactions = {
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@ -15,10 +15,14 @@
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-- You should have received a copy of the GNU Affero General Public License
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-- along with this program. If not, see <https://www.gnu.org/licenses/>.
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local tax_tables = {}
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-- Base income tax
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-- https://www.ato.gov.au/rates/individual-income-tax-rates/
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/itra1986174/sch7.html
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/itra1986174/s3.html (tax-free threshold)
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-- Maps each financial year to list of (upper limit (INclusive), flat amount, marginal rate)
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local base_tax = {
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tax_tables.base_tax = {
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[2025] = {
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{18200, 0, 0},
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{45000, 0, 0.16},
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@ -42,8 +46,114 @@ local base_tax = {
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}
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}
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local tax_tables = {
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base_tax = base_tax,
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-- FBT type 1 gross-up factor
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-- https://www.ato.gov.au/rates/fbt/#GrossupratesforFBT
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/fbtaa1986312/s5b.html
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tax_tables.fbt_grossup = 2.0802
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-- Medicare levy thresholds
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-- https://www.ato.gov.au/Individuals/Medicare-and-private-health-insurance/Medicare-levy/Medicare-levy-reduction/Medicare-levy-reduction-for-low-income-earners/
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/mla1986131/s3.html
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-- Maps each financial year to list of (lower threshold, upper threshold)
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tax_tables.medicare_levy_threshold = {
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[2025] = {27222, 34027},
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[2024] = {26000, 32500},
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[2023] = {24276, 30345},
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[2022] = {23365, 29207}
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}
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-- Medicare levy surcharge rates (singles)
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-- https://www.ato.gov.au/individuals-and-families/medicare-and-private-health-insurance/medicare-levy-surcharge/medicare-levy-surcharge-income-thresholds-and-rates
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-- https://www.austlii.edu.au/cgi-bin/viewdb/au/legis/cth/consol_act/mla1986131/s8b.html
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/phia2007248/s22.35.html
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/phia2007248/s22.45.html
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-- Maps each financial year to list of (upper limit (INclusive), MLS rate)
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-- FIXME: Only supports singles
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tax_tables.medicare_levy_surcharge_single = {
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[2025] = {
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{97000, 0},
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{113000, 0.01},
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{151000, 0.0125},
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{math.huge, 0.015}
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},
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[2024] = {
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{93000, 0},
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{108000, 0.01},
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{144000, 0.0125},
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{math.huge, 0.015}
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}
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}
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-- Study and training loan (HELP, etc.) repayment thresholds and rates
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-- https://www.ato.gov.au/Rates/HELP,-TSL-and-SFSS-repayment-thresholds-and-rates/
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/hesa2003271/s154.20.html
|
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-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/hesa2003271/s154.25.html
|
||||
-- https://www.austlii.edu.au/cgi-bin/viewdoc/au/legis/cth/consol_act/hesa2003271/s154.30.html
|
||||
-- Maps each financial year to list of (upper limit (EXclusive), repayment rate)
|
||||
tax_tables.study_loan_repayment_rates = {
|
||||
[2025] = {
|
||||
{54435, 0},
|
||||
{62851, 0.01},
|
||||
{66621, 0.02},
|
||||
{70619, 0.025},
|
||||
{74856, 0.03},
|
||||
{79347, 0.035},
|
||||
{84108, 0.04},
|
||||
{89155, 0.045},
|
||||
{94504, 0.05},
|
||||
{100175, 0.055},
|
||||
{106186, 0.06},
|
||||
{112557, 0.065},
|
||||
{119310, 0.07},
|
||||
{126468, 0.075},
|
||||
{134057, 0.08},
|
||||
{142101, 0.085},
|
||||
{150627, 0.09},
|
||||
{159664, 0.095},
|
||||
{math.huge, 0.1}
|
||||
},
|
||||
[2024] = {
|
||||
{51550, 0},
|
||||
{59519, 0.01},
|
||||
{63090, 0.02},
|
||||
{66876, 0.025},
|
||||
{70889, 0.03},
|
||||
{75141, 0.035},
|
||||
{79650, 0.04},
|
||||
{84430, 0.045},
|
||||
{89495, 0.05},
|
||||
{94866, 0.055},
|
||||
{100558, 0.06},
|
||||
{106591, 0.065},
|
||||
{112986, 0.07},
|
||||
{119765, 0.075},
|
||||
{126951, 0.08},
|
||||
{134569, 0.085},
|
||||
{142643, 0.09},
|
||||
{151201, 0.095},
|
||||
{math.huge, 0.1}
|
||||
},
|
||||
[2023] = {
|
||||
{48361, 0},
|
||||
{55837, 0.01},
|
||||
{59187, 0.02},
|
||||
{62739, 0.025},
|
||||
{66503, 0.03},
|
||||
{70493, 0.035},
|
||||
{74723, 0.04},
|
||||
{79207, 0.045},
|
||||
{83959, 0.05},
|
||||
{88997, 0.055},
|
||||
{94337, 0.06},
|
||||
{99997, 0.065},
|
||||
{105997, 0.07},
|
||||
{112356, 0.075},
|
||||
{119098, 0.08},
|
||||
{126244, 0.085},
|
||||
{133819, 0.09},
|
||||
{141848, 0.095},
|
||||
{math.huge, 0.1}
|
||||
}
|
||||
}
|
||||
|
||||
return tax_tables
|
||||
|
@ -13,6 +13,4 @@ pub type QuantityInt = i64;
|
||||
// Magic strings
|
||||
// TODO: Make this configurable
|
||||
pub const CURRENT_YEAR_EARNINGS: &'static str = "Current Year Earnings";
|
||||
pub const INCOME_TAX: &'static str = "Income Tax";
|
||||
pub const INCOME_TAX_CONTROL: &'static str = "Income Tax Control";
|
||||
pub const RETAINED_EARNINGS: &'static str = "Retained Earnings";
|
||||
|
Loading…
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Reference in New Issue
Block a user