GST Calculator

Select the add mode, enter the amount excluding GST, and the calculator applies the current Australian GST rate from the active rule pack to produce the GST amount and the GST-inclusive total. The rate is never hard-coded in the page. It is resolved from a versioned pack that cites the Australian Taxation Office, listed on the sources page with its retrieval date and content hash.

Select the remove mode and enter the GST-inclusive amount: the calculator divides by one plus the current rate to recover the GST-exclusive amount, then reports the GST component as the difference. Working backwards from an inclusive figure is not the same operation as applying the rate forward, which is why the two modes are separate rather than one field with a toggle. Both the divisor and the rounding are shown in the working.

Registration is required once your GST turnover reaches the relevant threshold, and the calculator displays the thresholds from its registration rule pack: a general threshold, a separate threshold for non-profit bodies, the number of days you have to register after reaching it, and the categories such as taxi and ride-sourcing that must register regardless of turnover. Those figures are reference-only and never feed the arithmetic on this page. The turnover test is applied to your current or projected twelve-month turnover, and registration itself is done with the Australian Taxation Office.

Because GST can be rounded at the line level or at the invoice total, and the two legitimately differ by cents on a multi-line invoice. The advanced mode makes that a choice: pick per-line or invoice-total rounding and the calculator allocates the rounded total back across the lines by largest remainder, so the lines always reconcile to the total shown. The rounding level in use is stated with the result.

That classification comes from the GST law and how it applies to your particular supply, so the calculator treats it as your selection rather than inferring it from an item description. Marking a line GST-free or input taxed excludes it from the GST calculation but keeps it in the invoice total. Entitlement to input tax credits on your purchases is a separate question that this calculator does not assess.

It depends on whether the contractor is registered for GST, which turns on the registration turnover thresholds shown in the calculator and on the categories that must register regardless of turnover. Where GST applies it is quoted on top of the fee and passed on to the Australian Taxation Office, so it is not part of what the contractor earns. The contractor day rate calculator keeps GST separate from income for exactly that reason.