Gross-Up Mistakes Australians Make and How to Avoid Them

Updated 1 September 2026 · Business and gst

A Gross-Up 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 Gross-Up calculations in Australia, and how to avoid them.

1. Forgetting on-costs

An employee costs well above their salary once super, workers comp and payroll tax are included.

2. Mixing up margin and markup

A 50% markup is a 33% margin. Pricing with the wrong one can erase profit.

3. Spending GST collected

GST belongs to the ATO. Keep it aside until your BAS is due.

4. Undercharging as a contractor

Your rate must cover super, leave, unbilled time and business costs, not just the salary you want.

5. Overlooking the detail that matters most here

Use your marginal rate plus the Medicare levy for personal income.

How the gross amount required changes with tax rate

A common mistake is getting one input slightly wrong. Here is what happens to the gross amount required when “Tax rate (%)” is off by up to 20% in either direction, with everything else held steady.

Tax rate (%)	Gross amount required
24	$1,315.79
27	$1,369.86
30	$1,428.57
33	$1,492.54
36	$1,562.50

At 24 the result is $1,315.79; at 36 it is $1,562.50. 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

Gross = net ÷ (1 − tax rate). With typical inputs the calculator returns gross amount required of $1,428.57. 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.