Australian GST Calculator (10%) with Invoice Check Widget
Work out Australian GST the way the GST Act defines it - 10% on top or one-eleventh of a GST-inclusive price - and total an invoice with taxable and GST-free lines, then see exactly what the ATO requires on the tax invoice for that amount.
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How it works
Section 9-70 of the GST Act makes the GST on a taxable supply 10% of its value, and s 9-75 makes the value the price less the GST, so adding GST multiplies by 1.1 and the GST inside an inclusive price is one-eleventh of it - the Act's own $22,000 car carries $2,000. Invoice mode reads one line per item in the form item | amount | taxable or GST-free, with amounts entered either before GST or GST-inclusive. Each taxable line's GST is rounded to the nearest cent and the lines are added; GST-free lines such as basic food carry none. The checklist then follows the ATO's tax-invoice page: no invoice is needed at $82.50 or less including GST, seven details are required under $1,000, and $1,000 or more also needs the buyer's identity or ABN. The words "Total price includes GST" are offered only when the GST is exactly one-eleventh of the total. Unlike the generic VAT calculator, the rate is fixed at Australia's 10% and GST-free lines are supported.
Calculation method
- Add GST: GST = 10% x price before GST; total = 1.1 x price
- Remove GST: GST = GST-inclusive price / 11; price before GST = price - GST
- Invoice: GST per taxable line rounded to the cent; GST total = sum of lines; GST-free lines add 0
- Tax invoice: none required at <= $82.50 incl. GST; 7 details under $1,000; + buyer identity or ABN at >= $1,000
Worked examples
Adding GST
Inputs: Add GST to $100
Result: Price including GST $110.00; GST $10.00
10% of $100.
The Act's example
Inputs: Take GST out of $22,000
Result: GST included $2,000.00; price before GST $20,000.00
$22,000 / 11 = $2,000 (GST Act s 9-75 example).
Mixed invoice
Inputs: Website design 1,200 taxable; domain renewal 30 taxable; bread 45 GST-free; amounts before GST
Result: GST total $123.00; invoice total $1,398.00; buyer's identity or ABN required
120 + 3 + 0 = 123; the total is $1,000 or more.
General information for Australian GST, not tax advice. Check with the ATO or your tax agent for your circumstances.
Limitations
- It does not decide whether an item is taxable, GST-free or input-taxed; the user marks each line.
- GST is rounded per line to the cent; an accounting system that rounds per invoice can differ by a cent or two.
- Margin scheme, wine equalisation tax, luxury car tax and imported goods are not modelled.
- Up to 200 invoice lines.
Where publishers use it
- An Australian freelancer's pricing page showing rates before and after GST
- A bookkeeping blog post on reading a mixed taxable and GST-free supermarket invoice
- A tradie's quote page converting a GST-inclusive quote back to the ex-GST amount
- A small-business course module on what a valid tax invoice must contain
- An online store's wholesale page that lists GST-free food alongside taxable items
Questions
How do I take GST out of a price?
Divide the GST-inclusive price by 11. A $22,000 price includes $2,000 GST and $20,000 before GST - the example in s 9-75 of the GST Act. Multiplying by 10% would give the wrong answer ($2,200).
When must I give a tax invoice?
If a customer asks, within 28 days - unless the sale is $82.50 or less including GST. Below $1,000 the invoice needs seven details; at $1,000 or more it must also show the buyer's identity or ABN.
What are the seven details?
That it is intended to be a tax invoice, the seller's identity, the seller's ABN, the date, a description with quantity and price, the GST amount (or 'Total price includes GST' when GST is exactly 1/11), and the extent to which each sale is taxable.
What counts as GST-free?
Common examples are basic food, many health and education services and exports. This widget does not classify items - you mark each line taxable or GST-free yourself.
How is this different from the VAT calculator?
The VAT calculator takes any rate for a single price. This one fixes Australia's 10% rate, handles a whole invoice with GST-free lines and applies the ATO's tax-invoice thresholds.
Sources
- A New Tax System (Goods and Services Tax) Act 1999 - Federal Register of Legislation . s 9-70 (GST is 10% of the value of a taxable supply) and s 9-75 with its $22,000 / $2,000 example; compilation C2026C00081 of 1 January 2026. Checked 2026-10-01.
- Tax invoices - Australian Taxation Office . 28-day rule, $82.50 threshold, the seven details under $1,000 and the buyer's identity or ABN at $1,000 or more. Page updated 18 September 2026; checked 2026-10-01.
- How GST works - Australian Taxation Office . GST is a broad-based tax of 10%; GST-free sales. Checked 2026-10-01.
Cite or recommend this tool
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A2Z Tools Australian GST Calculator (10%) with Invoice Check https://a2z.tools/embed/au-gst-calculator
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Australian GST Calculator (10%) with Invoice Check by A2Z Tools - https://a2z.tools/embed/au-gst-calculator
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