Add or remove 10% GST in one step. Free Australian GST calculator, plus the $75,000 registration rule, the divide-by-11 trick and a worked BAS example.
Last reviewed October 2026 by Megan Birot, Content Editor, OurTop10. Figures checked against the sources named on this page.
What changed (29 September 2026): new page. Calculator built and checked against the ATO’s 1/11 rule for working out the GST inside a price.
Add 10% GST to $1,000.00 and the price becomes $1,100.00. The GST part is $100.00.
- GST in Australia is a flat 10% on most goods and services. To add it, multiply by 1.1. To find the GST inside a price, divide by 11.
- You must register for GST once your business turnover reaches $75,000 a year ($150,000 for not-for-profits). Taxi and rideshare drivers register from the first dollar.
- A $1,100 invoice contains $100 of GST. A $75,000 turnover business collects roughly $7,500 of GST a year and pays it to the ATO through its BAS, less the GST it paid on its own costs.
Jump to: How the 10% works · Who has to register · What is GST-free · Worked example · FAQs
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GST is 10% of the price before tax, so a $500 job becomes $550 with GST, and a $550 invoice has $50 of GST inside it. The calculator above does both directions; the rest of this page covers when you have to charge it, what is GST-free, and how the numbers flow through your BAS.
How the 10% works
Adding GST means multiplying the before-tax price by 1.1. Removing it is the part people get wrong: you do not take 10% off the total, you divide the total by 11 to find the GST, because the 10% was added to a smaller number. The ATO calls this the 1/11th rule.
| You know | To get | Do this | Example |
|---|---|---|---|
| Price before GST | Price with GST | Multiply by 1.1 | $1,000 becomes $1,100 |
| Price with GST | GST amount | Divide by 11 | $1,100 has $100 of GST |
| Price with GST | Price before GST | Divide by 1.1 | $1,100 was $1,000 before GST |
Source: ato.gov.au, GST and the 1/11th rule (page checked 29 September 2026).
Who has to register for GST
You must register for GST when your business has, or expects to have, GST turnover of $75,000 or more in a 12-month period. Not-for-profit organisations get a higher line of $150,000. Anyone providing taxi, limousine or rideshare travel has to register no matter how small the income. Below the line, registering is optional, and some businesses do it so they can claim back the GST on their own purchases.
- Registration is free and done through the ATO’s Business Portal or your accountant, usually with your ABN.
- Once registered you charge GST on taxable sales, claim credits on business purchases, and report the difference on a Business Activity Statement (BAS), normally every quarter.
- Register late and the ATO can ask for GST on sales you made from the date you should have registered, even though you never collected it.
Source: ato.gov.au, Registering for GST (thresholds current for 2026-27, checked 29 September 2026).
What is GST-free
Most basic food, most health and medical services, most education courses, childcare, exports and some financial supplies carry no GST. Residential rent is input-taxed, which means no GST is charged and the landlord cannot claim credits on related costs either. If your business sells a mix, the calculator applies only to the taxable part.
Worked example: a sole trader’s first GST quarter
A Sydney electrician invoices $30,000 (plus GST) in a quarter and spends $9,000 (including GST) on materials and fuel from GST-registered suppliers.
| Item | Amount | GST |
|---|---|---|
| Sales invoiced ($30,000 + GST) | $33,000 | $3,000 collected |
| Business purchases (GST inclusive) | $9,000 | $818 credit ($9,000 ÷ 11) |
| Net GST payable on the BAS | $2,182 |
OurTop10 calculation, 29 September 2026. Assumes every purchase was a taxable supply from a GST-registered seller with a valid tax invoice, and no GST-free sales.
What to do next
If you have just crossed the $75,000 line, the next job is picking who does your BAS. Our guide to what accountants charge has the going rates for BAS lodgement and bookkeeping, and the OurTop10 shortlists of vetted Sydney accountants, Melbourne accountants and Brisbane accountants are the place to compare them. For tax on the profit itself, use the income tax calculator.
FAQs
How do I work out GST from a total?
Divide the GST-inclusive total by 11. A $2,200 total contains $200 of GST, and the price before GST was $2,000. Taking 10% off the total ($220) gives the wrong answer.
Do I charge GST if I earn under $75,000?
Only if you have chosen to register. If you are not registered you must not add GST to invoices or call them tax invoices. Once turnover reaches $75,000 in any rolling 12 months, you have 21 days to register.
Is GST charged on the price before or after a discount?
After. GST applies to the amount the customer actually pays, so a $1,000 item discounted to $900 carries $90 of GST, and the invoice total is $990.
Can I claim GST back on business purchases?
Yes, if you are registered, the purchase was for business use, and you hold a tax invoice for anything over $82.50. The credit reduces what you pay on your BAS, and can produce a refund in a quarter where you bought more than you sold.
Is GST-inclusive pricing compulsory?
For prices shown to consumers, yes. Australian Consumer Law requires the displayed price to be the total the customer pays, including GST. Business-to-business quotes can be shown as “plus GST” as long as that is clear.
Sources
- Australian Taxation Office, Registering for GST: ato.gov.au
- Australian Taxation Office, When to charge GST (and when not to): ato.gov.au
- Australian Taxation Office, Tax invoices: ato.gov.au
- Australian Competition and Consumer Commission, Displaying prices: accc.gov.au
Megan Birot is OurTop10’s Content Editor. She holds a Certificate IV in Finance and Mortgage Broking (FNS40821) and a Diploma of Finance and Mortgage Broking Management (FNS50322), and checks every guide and calculator on the site against current ATO rules, lender policy and state revenue office thresholds before it goes live. She also runs the editorial reviews on OurTop10’s broker, accountant, conveyancer and buyer’s agent shortlists, and writes all the media releases for the OurTop10 Reports.