data tool
GST calculator for Australia
To add GST in Australia, multiply the price by 1.1; to take it out of a GST inclusive price, divide by 11 to get the GST. This calculator does both line by line, keeps GST free items at zero, rounds to the cent the way the ATO describes, and says when a customer can ask for a tax invoice.
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- Runs on your device, nothing is uploaded
- Free, no sign in
- No watermark, no file limit
How it works
- 1
Choose the direction
Pick whether the amounts you type exclude GST, so it is added, or include it, so it is taken out.
- 2
Enter each line
Type an amount per line and set it to 10% GST or GST free. Add lines up to 20 for a whole invoice.
- 3
Read the totals
The panel shows the total excluding GST, the GST and the total including GST, rounded to the cent.
- 4
Check the invoice note
Below the lines, a note says whether the sale is over $82.50, when a tax invoice is owed on request, and over $1,000, when it must show the buyer.
Dividing by 11, and why it is not 10%
GST in Australia is 10% of the price before tax. Once GST has been added, it makes up one eleventh of the total, not one tenth, because the total is 110% of the original price. So the GST in a $110 price is $10, which is 110 divided by 11, while 10% of $110 would wrongly give $11. The same arithmetic works for any GST inclusive amount: divide by 11 for the GST, or divide by 1.1 for the price before GST. Multiplying by 1.1 goes the other way and adds the tax to a price that does not include it.
GST free lines on one invoice
Many invoices mix taxable and GST free items, such as a cafe selling fresh fruit and prepared meals, or a medical practice selling a consultation and a cosmetic product. Each line needs its own treatment, and the invoice must show which items are taxable. In this calculator each line has its own rate, so a GST free line contributes its amount to the totals with no GST. Lines at 10% are added together and the GST is worked out on their combined value, which matches the ATO's total invoice approach when every taxable item is exactly one eleventh GST.
When a tax invoice is owed
A business registered for GST must give a tax invoice within 28 days when a customer asks for one, unless the sale is $82.50 or less including GST. A tax invoice under $1,000 must show that it is a tax invoice, the seller's identity and ABN, the date, what was sold with quantities and prices, the GST, and how much of each item is taxable. From $1,000 it must also show the buyer's identity or ABN. The note under the calculator applies these two thresholds to the total you type.
Rounding to the cent
GST is worked out to the cent, rounding half a cent up. When an invoice has one taxable sale, the GST is rounded once. When it has several, the ATO allows either totalling first and rounding once, or working out each sale's GST and then rounding the total. Rounding each line separately and adding the rounded figures can drift a cent or two on long invoices. This tool totals the lines at each rate and rounds once, so the invoice total matches the total invoice rule. A small difference from an accounting system that rounds per line is normal.
Putting GST on a quote or invoice
A quote should say whether its prices include GST, because a customer who reads $4,400 and later sees $4,840 has every reason to be annoyed. Show the total excluding GST, the GST and the total including GST, or write that all prices include GST. The proposals module labels tax as GST when a quote or invoice is in Australian dollars, which is its default currency, and its pricing table has a tax column on each line, so the split this calculator shows carries straight into the document a client signs.
Registering for GST
Businesses with a GST turnover of $75,000 or more, or $150,000 for non profit bodies, must register for GST; taxi, limousine and ride sourcing drivers must register regardless of turnover. Below the threshold registration is optional, and an unregistered business must not charge GST or issue tax invoices. If you are not registered, use the GST free option on every line or leave GST out of your prices altogether.
Limits
- Rates checked on 21 October 2026 against the A New Tax System (Goods and Services Tax) Act 1999 and the ATO. This is arithmetic, not tax advice.
- Lines at the same rate are added up before the GST is worked out, then rounded once to the nearest cent, half a cent up. Per line amounts are shown for reference.
- No BAS, no margin scheme, no import GST and no wine equalisation tax.
- Whether an item is GST free is your call; the tool only applies the choice you make.
What it does not do
- It does not lodge or prepare a BAS.
- It does not decide whether you must register for GST.
- It does not store the amounts.
Questions people ask
How do I work out GST from a total price?
Divide the GST inclusive total by 11 to get the GST. For a $275 total, the GST is $25 and the price before GST is $250. Dividing by 1.1 gives the GST exclusive price directly. Taking 10% of the total gives the wrong answer, because the total already has the tax in it.
Is GST in Australia always 10%?
The rate in the GST Act is 10%, and it has not changed since GST began in July 2000. Some supplies are GST free, such as most basic food, some health and education services and exports, and some are input taxed, such as residential rent and many financial supplies, so not every sale carries 10%.
Do I charge GST if I am not registered?
No. A business that is not registered for GST must not add GST to its prices or issue tax invoices. You must register once your GST turnover reaches $75,000 a year, or straight away if you provide taxi or ride sourcing services. Registration below the threshold is optional.
How do I show GST free items on an invoice?
List each item with its price, show which items are taxable, and show the GST amount for the taxable ones. A simple way is a GST column with 10% or GST free on each line, then a total GST line. The ATO requires the invoice to show the extent to which each sale is taxable.
Can a customer demand a tax invoice for a small sale?
Only for sales over $82.50 including GST. At or under that amount a registered business does not have to provide a tax invoice, and the buyer can still claim the GST credit using their own records such as a receipt. Over $82.50, the business must provide one within 28 days of the request.
Why does my accounting software show one cent different?
Rounding order. Software that rounds GST on every line and then adds the lines can end up a cent away from a calculation that adds the lines first and rounds once. Both are acceptable under the ATO's rules for invoices with several taxable sales, provided the method is applied consistently.
Put the GST split on a quote
Take what you made here into proposals.
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Background reading: the question page on this.
Written and checked by the OneCraft team. Last checked .