Mathematics Standard • Year 11 • Module 3 • Lesson 6
Deductions and Net Pay
Apply deduction rules to realistic Australian workplace scenarios — classify each component, calculate, conclude.
Problem 1 — Carpenter's weekly take-home
Bao is a self-employed carpenter (working as a wage-earner for an agency this month). His ordinary rate is $38.50/hr. This week he worked 38 ordinary hours and 4 hours of overtime at time-and-a-half. His deductions are: PAYG tax $452, salary sacrifice super $85, union fees $15.50.
Set up: What are we solving for?
(i) Calculate Bao's gross weekly pay. 2 marks
(ii) Calculate Bao's total deductions. 1 mark
(iii) Calculate Bao's net weekly pay (take-home). 1 mark
Stuck? Calculate gross first (ordinary + overtime), then sum deductions, then subtract.Problem 2 — Classify employer cost vs employee deduction
A new junior accountant has a confusing pay record. Here are 6 items from her weekly payroll:
A) PAYG tax withheld $268.00
B) Employer super guarantee at 11.5% (calculate)
C) Salary sacrifice super (employee chose) $50.00
D) Union fees $14.00
E) Gross wage for the week $1,480.00
F) Employer-paid workers' compensation insurance (not paid from her wage) $22.00
Set up: What are we solving for?
(i) List the letters of the items that should be subtracted from gross pay when calculating net pay. 2 marks
(ii) Calculate the employer super guarantee for the week. 1 mark
(iii) Calculate (a) the worker's net weekly pay, and (b) the total weekly cost to the employer (wage + employer super + workers' comp). 3 marks
Stuck? Employer super and workers' comp are EMPLOYER costs, not employee deductions.Problem 3 — Reverse-calculate gross from net
Mei works at a council depot. Her weekly bank deposit (net pay) is $1,182.40. Her payslip lists PAYG tax of $312.60 and salary sacrifice super of $90.00.
Set up: What are we solving for?
(i) Calculate her total weekly deductions. 1 mark
(ii) Calculate her gross weekly pay using the reverse formula (Gross = Net + Deductions). 2 marks
(iii) Calculate her gross annual pay. 1 mark
Stuck? Annual = Weekly gross × 52.Problem 4 — Percentage tax + flat deductions
Connor earns $1,920 gross per week. His employer withholds PAYG tax at 24% of gross. He also has $42 weekly union fees and $60 weekly salary sacrifice super.
Set up: What are we solving for?
(i) Calculate the PAYG tax withheld for the week. 1 mark
(ii) Calculate his total weekly deductions. 1 mark
(iii) Calculate his net weekly pay, and express it as a percentage of his gross weekly pay (to 1 decimal place). 3 marks
Stuck? Calculate tax as decimal × gross, then sum deductions, then subtract.Problem 5 — How much does this hire really cost?
A small business owner is hiring a new bookkeeper. She wants to know the true cost. The hire offer is:
Gross salary: $68,000 per year.
Employer super guarantee: 11.5%.
Workers' compensation insurance (employer-paid): $1,680 per year.
Annual training budget per staff (employer-paid): $900 per year.
Set up: What are we solving for?
(i) Calculate the employer's super contribution for the year. 1 mark
(ii) Calculate the total true annual cost to the employer (salary + super + workers' comp + training). 2 marks
(iii) The bookkeeper's view: the worker thinks she "costs the employer $68,000 per year." State in one sentence by how much this underestimates the true cost. 2 marks
Stuck? True cost = salary + employer super + workers' comp + training. The $68,000 alone is just the wages line.How did this worksheet feel?
What I'll revisit before next class:
Problem 1 — Bao's take-home pay
Set up. Gross = ordinary + overtime; net = gross − total deductions.
(i) Ordinary = $38.50 × 38 = $1,463.00. OT rate = $38.50 × 1.5 = $57.75/hr → OT pay = $57.75 × 4 = $231.00. Gross = $1,463.00 + $231.00 = $1,694.00.
(ii) Total deductions = $452.00 + $85.00 + $15.50 = $552.50.
(iii) Net = $1,694.00 − $552.50 = $1,141.50.
Problem 2 — Classify items + calculate
Set up. Identify which items are subtracted from gross to give net (employee deductions only).
(i) Subtracted from gross: A (PAYG), C (salary sacrifice super), D (union fees). Employer-paid (NOT subtracted): B, F. E is gross itself.
(ii) Employer super = $1,480 × 0.115 = $170.20.
(iii) (a) Net = $1,480 − ($268 + $50 + $14) = $1,480 − $332 = $1,148.00. (b) Employer total cost = $1,480 (wage) + $170.20 (super) + $22.00 (workers' comp) = $1,672.20.
Problem 3 — Reverse calc to gross
Set up. Gross = Net + Total deductions, then × 52 for annual.
(i) Total deductions = $312.60 + $90.00 = $402.60.
(ii) Gross weekly = $1,182.40 + $402.60 = $1,585.00.
(iii) Gross annual = $1,585.00 × 52 = $82,420.00.
Problem 4 — Percentage tax + flat deductions
Set up. Compute the tax as decimal × gross, then sum the deductions, subtract.
(i) PAYG = $1,920 × 0.24 = $460.80.
(ii) Total deductions = $460.80 + $42 + $60 = $562.80.
(iii) Net = $1,920 − $562.80 = $1,357.20. As a percentage: $1,357.20 ÷ $1,920 × 100 = 70.687... ≈ 70.7% of gross.
Problem 5 — True hire cost
Set up. Total employer cost = salary + super + workers' comp + training.
(i) Employer super = $68,000 × 0.115 = $7,820.00.
(ii) True cost = $68,000 + $7,820 + $1,680 + $900 = $78,400.00 per year.
(iii) $78,400 − $68,000 = $10,400. The "$68,000" view underestimates the true annual cost by $10,400 per year — this is the on-cost (super + insurance + training) that the employer pays in addition to the wage.