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hscscience Maths Std · Y11
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Module 3 · L8 of 14 ~55 min MS-F1 ⚡ +90 XP available

Calculating Income Tax

Australia uses a progressive tax system, the more you earn, the higher the rate you pay on each extra dollar. But only the income in each bracket gets taxed at that bracket's rate, not your entire income. If you earn $\$90{,}000$, you are NOT paying 30% on all of it.

Today's hook, If you earn $\$90,000$, are you paying 30% tax on the whole amount? Or only on the part above $\$45,000$? Think about what progressive means before we start.
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Three printable worksheets that build from foundations to mastery, or build your own from any module’s questions.

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Three printable worksheets that build from foundations to mastery, or build your own from any module’s questions.

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Recall, your gut answer first
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Australia uses a progressive tax system, the more you earn, the higher the rate you pay on each extra dollar. But here's the key word: progressive means only the income in each bracket gets taxed at that bracket's rate, not your entire income.

Before we apply any numbers think about what that actually means in dollars, and why a government might design a tax system this way rather than charging everyone the same flat percentage.

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The key relationships you need to own
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Four formulas drive every income tax calculation. The most important skill is choosing the right bracket and applying it correctly.

$$\text{Income tax} = \text{Base amount} + \text{Marginal rate} \times (\text{Taxable income} - \text{Threshold})$$

$$\text{Medicare levy} = \text{Taxable income} \times 0.02$$

$$\text{Total tax liability} = \text{Income tax} + \text{Medicare levy}$$

$$\text{Refund} = \text{PAYG withheld} - \text{Total tax liability} \quad (\text{when PAYG} > \text{liability})$$

Tax calculation sequence migrated to sequence layout
Debt = Total tax liability − PAYG withheld (when liability > PAYG)
Marginal rate, only on the excess
The marginal rate applies ONLY to income above the bracket threshold. A $\$70,000$ income: 30% applies only to the $\$25,000$ above $\$45,000$, not to the full $\$70,000$.
Medicare levy, on taxable income
Medicare levy = 2% of taxable income (not of income tax). For $\$70,000$: Medicare = $\$70,000$ × 0.02 = $\$1,400$, not $\$11,788$ × 0.02.
6-step strategy
1. Find bracket. 2. Write base amount. 3. Subtract threshold from income. 4. Apply marginal rate. 5. Add base. 6. Add Medicare levy separately.
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What you'll master
Know

Key facts

  • The 2024–25 Australian income tax brackets and how to read them
  • That Medicare levy = 2% of taxable income, added separately
  • The formulas for tax refund and tax debt
Understand

Concepts

  • Why the marginal rate applies only to income above the bracket threshold
  • Why effective tax rate is always lower than the marginal rate
  • How PAYG withholding is reconciled against actual tax liability at year end
Can do

Skills

  • Calculate income tax from a tax table for any taxable income
  • Add Medicare levy to find total tax liability
  • Determine whether a worker receives a refund or owes a debt, and by how much
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Key terms
Progressive TaxA tax system where higher income earners pay a higher percentage of their income in tax.
Marginal Tax RateThe rate of tax applied to the last dollar earned within a particular tax bracket.
Tax BracketA range of income that is taxed at a particular rate.
Tax PayableThe total amount of income tax owed to the government before offsets.
Medicare LevyAn additional charge on taxable income that funds Australia's universal health system. Use 2% as the supplied classroom rule; in practice reductions and exemptions apply to some taxpayers.
Effective Tax RateTotal tax liability divided by taxable income, always lower than the marginal rate in a progressive system.
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How progressive tax brackets work

In a progressive tax system, each portion of income is taxed at a different rate, higher rates apply only to the income within...

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How progressive tax brackets work
core concept

In a progressive tax system, each portion of income is taxed at a different rate, higher rates apply only to the income within that bracket, not to total income.

The supplied resident income tax table for 2024–25 (unchanged for 2025–26). Always work from the table given in the question, tax rates change between years:

  • $\$0$ – $\$18{,}200$: 0% (nil)
  • $\$18{,}201$ – $\$45{,}000$: 16c for each $\$1$ over $\$18,200$ (base: $\$0$)
  • $\$45{,}001$ – $\$135{,}000$: $\$4,288$ + 30c for each $\$1$ over $\$45{,}000$
  • $\$135{,}001$ – $\$190{,}000$: $\$31,288$ + 37c for each $\$1$ over $\$135{,}000$
  • $\$190{,}001$+: $\$51{,}638$ + 45c for each $\$1$ over $\$190,000$
Each marginal rate applies only to the income within its bracket.
Always use taxable income, not gross income: The tax table is applied to taxable income (after deductions). Using gross income gives a higher, and incorrect, tax figure.
Medicare levy is 2% of taxable income, not of tax payable: For a $\$70,000$ income: correct Medicare = $\$70,000$ × 0.02 = $\$1,400$. Incorrect = $\$11,788$ × 0.02 = $\$235.76$. A very different result.

Progressive tax: each bracket’s rate applies only to the income within that slice, not the whole income. Tax = fixed amount for lower brackets already taxed + (income − bracket lower limit) × marginal rate. Never apply the highest rate to the entire income.

Pause, copy the bracket tax formula (tax = base amount + marginal rate × (taxable income − bracket lower limit)), the Medicare levy formula (taxable income × 0.02), and the total liability formula (income tax + Medicare levy) into your book.

Quick check: What is the Medicare levy on a taxable income of $\$45{,}000$?

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Tax refund or tax debt, reconciling PAYG

We just saw that progressive tax brackets work by applying each rate only to the income within that slice, tax = fixed base...

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Tax refund or tax debt, reconciling PAYG
core concept

We just saw that progressive tax brackets work by applying each rate only to the income within that slice, tax = fixed base amount + marginal rate × (income − bracket lower limit). That raises a question: your employer withholds PAYG tax each pay period during the year, how do you compare that to the actual tax calculated at year end to find out if you get a refund or owe more? This card answers it → refund = PAYG withheld − total tax liability (when PAYG > liability); tax debt = total tax liability − PAYG withheld (when liability > PAYG).

At the end of each financial year, Australians lodge a tax return comparing what was withheld by their employer against what they actually owe, the difference is either a refund or a debt.

Migrate refund vs debt decision diagram to comparison-table
Compare PAYG to total tax liability, not income tax alone: The comparison is always: PAYG withheld vs total tax liability (income tax + Medicare levy combined). Forgetting to include the Medicare levy before comparing understates the liability.

PAYG withholding = tax paid during the year via employer. Tax owed = actual tax calculated at year end. Refund if PAYG > tax owed; tax debt if PAYG < tax owed. Net refund = PAYG withheld − tax owed (positive = refund, negative = debt).

Pause, copy the PAYG reconciliation formula: if PAYG withheld > tax owed → refund = PAYG − tax owed; if tax owed > PAYG → debt = tax owed − PAYG, and the reasonableness check (effective rate = total tax ÷ taxable income; should be approximately 20–30% for incomes around $\$60\text{k}$–$\$100\text{k}$) into your book.

True or false: If PAYG withheld ($\$14,000$) is less than total tax liability ($\$15,200$), the taxpayer receives a refund of $\$1{,}200$.

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Worked examples · 4 in a row, reveal as you go

Worked examples · 4 in a row, reveal as you go

Worked examples · 4 in a row, reveal as you go

PROBLEM 1 · FULL TAX CALCULATION, REFUND

Zara has a taxable income of $\$67,500$ for the 2024–25 financial year. Her employer withheld $\$14,980$ in PAYG tax. Calculate: (a) income tax payable, (b) Medicare levy, (c) total tax liability, and (d) whether she receives a refund or owes a debt, and by how much.

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$\$67{,}500$ falls in the $\$45{,}001$–$\$135{,}000$ bracket
Identify the correct bracket from the tax table, write this line first.
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PROBLEM 2 · TAX DEBT OUTCOME

Marcus has a taxable income of $\$112,000$. His PAYG withheld for the year was $\$25,300$. Calculate his total tax liability and determine whether he has a refund or debt.

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$\$112{,}000$ falls in the $\$45{,}001$–$\$135{,}000$ bracket
Identify the correct bracket.
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PROBLEM 3 · FULL QUESTION, INCOME TO REFUND/DEBT

Priya earns $\$82,600$ salary and $\$1,200$ in bank interest. Her allowable deductions total $\$2,850$. Her PAYG withheld was $\$19,400$. Calculate her tax refund or debt.

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$\text{Gross income} = \$82{,}600 + \$1{,}200 = \$83{,}800$
Sum all assessable income.
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PROBLEM 4 · BRACKET BOUNDARY CHECK

Ella has a taxable income of $\$45,000$ exactly. Her PAYG withheld for the year was $\$5,100$. Calculate her income tax, Medicare levy, total tax liability, and whether she receives a refund or owes a debt.

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$\$45{,}000$ is at the top of the $\$18{,}201$–$\$45{,}000$ bracket
Use the 16c per dollar over $\$18{,}200$ rule.
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Fill the gap: A taxpayer has taxable income of $\$60,000$. Income tax (bracket) = $\$4,288$ + 0.30 × ($\$60{,}000$ − $\$45{,}000$) = $\$$.

Match each taxable income to the correct bracket.

  • $\$12{,}000$
  • $\$35{,}000$
  • $\$80{,}000$
  • $\$150{,}000$
  • $\$45{,}001$–$\$135{,}000$ (30%)
  • $\$135{,}001$–$\$190{,}000$ (37%)
  • $\$0$–$\$18{,}200$ (nil)
  • $\$18{,}201$–$\$45{,}000$ (16%)
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Revisit your thinking

Look back at what you wrote in the Think First section.

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Revisit your thinking

Look back at what you wrote in the Think First section. Progressive tax means that earning $\$90,000$ puts you in the $\$45,001$–$\$135,000$ bracket, but the 30% rate applies only to the $\$45,000$ above the threshold, not to the full $\$90{,}000$. Governments use progressive systems because they place a larger burden on those with greater ability to pay.

What has changed? What did you get right? What surprised you?

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Top 3 list: Name THREE things you must do correctly to get the right tax refund/debt answer in an HSC question.

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Show what you have learned

Multiple choice, then short answer under exam conditions.

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Multiple choice
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Pick your answer, then rate your confidence. That tells the system what to drill next.

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Short answer
ApplyBand 32 marks

SA 1. A taxpayer has taxable income of $\$60{,}000$. Calculate their income tax payable before Medicare levy. (2 marks)

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ApplyBand 33 marks

SA 2. A taxpayer has taxable income of $\$72,000$. Their PAYG withheld for the year was $\$15,600$. Calculate their total tax liability including Medicare levy, and determine whether they receive a refund or owe a debt. (3 marks)

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ApplyBand 43 marks

SA 3. A taxpayer's taxable income is $\$95,000$ and PAYG withheld was $\$20,000$. Calculate whether they receive a refund or owe a debt. (3 marks)

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📖 Answers (click to reveal)

SA 1 (2 marks): Bracket: $\$45{,}001$–$\$135{,}000$ [1]. Income tax = $\$4{,}288$ + 0.30 × ($\$60{,}000$ − $\$45{,}000$) = $\$4{,}288$ + $\$4{,}500$ = $\$8{,}788.00$ [1].

SA 2 (3 marks): Income tax = $\$4{,}288$ + 0.30 × ($\$72{,}000$ − $\$45{,}000$) = $\$12{,}388$ [1]. Medicare levy = $\$72{,}000$ × 0.02 = $\$1{,}440$ [1]. Total liability = $\$13,828$. Refund = $\$15,600$ − $\$13{,}828$ = $\$1{,}772$ refund [1].

SA 3 (3 marks): Income tax = $\$4{,}288$ + 0.30 × ($\$95{,}000$ − $\$45{,}000$) = $\$19{,}288$ [1]. Medicare levy = $\$95{,}000$ × 0.02 = $\$1{,}900$ [1]. Total liability = $\$21,188$. Debt = $\$21,188$ − $\$20{,}000$ = $\$1{,}188$ debt [1].