Common Salary Sacrifice Mistakes (and a Better Way)

Updated 12 June 2026 · Tax and pay

A Salary Sacrifice Calculator gives a fast answer, but the answer is only as good as what goes in. These are the mistakes we see most often with salary sacrifice calculations in Australia, and how to avoid them.

1. Using last year’s tax rates

Brackets and offsets change. The Stage 3 changes from 1 July 2024 and further cuts from 1 July 2026 mean older figures can be well off.

2. Treating a deduction as a refund

A $1,000 deduction reduces taxable income by $1,000. The cash benefit is only your marginal rate on that amount.

3. Confusing marginal and average tax rates

Moving into a higher bracket only raises the tax on the dollars above that threshold. Your average rate is always lower than your marginal rate.

4. Forgetting the Medicare levy

Most take-home pay estimates that leave out the 2% levy overstate pay by hundreds or thousands of dollars.

5. Overlooking the detail that matters most here

Keep total concessional contributions, including your employer’s super guarantee, under the annual cap or the excess is taxed at your marginal rate.

How the net gain to your wealth changes with amount sacrificed to super per year

A common mistake is getting one input slightly wrong. Here is what happens to the net gain to your wealth when “Amount sacrificed to super per year ($)” is off by up to 20% in either direction, with everything else held steady.

Amount sacrificed to super per year ($)	Net gain to your wealth
8,000	$1,360.00
9,000	$1,530.00
10,000	$1,700.00
11,000	$1,870.00
12,000	$2,040.00

At 8,000 the result is $1,360.00; at 12,000 it is $2,040.00. If a small change in this input moves the answer a lot, it is worth double-checking that figure before you rely on the result.

A quick sense check

Sacrificed pay is taxed at 15% inside super instead of your marginal rate. The gain is (sacrifice × 0.85) − (the drop in your after-tax pay). With typical inputs the calculator returns net gain to your wealth of $1,700.00. If your own result looks wildly different, check that each figure is in the right unit and period (weekly, monthly or yearly) before drawing conclusions.