How to Calculate GST in Australia (2026): Formulas, Worked Examples and BAS Rules

Pricing a new product, checking a supplier's bill or getting ready for your first BAS? You'll need to calculate GST in Australia correctly — and know when it applies at all. This guide is for sole traders, small business owners and bookkeepers. It covers the two formulas (add 10% and divide by 11), worked Australian-dollar examples, who must register, which sales are GST-free or input-taxed, what a valid tax invoice needs, and how GST flows onto your business activity statement.

Quick answer

Australian GST is 10% of the GST-exclusive price. Add GST: price × 1.1. Find the GST in a GST-inclusive price: total ÷ 11. Remove GST: total ÷ 1.1. Register within 21 days once your GST turnover reaches A$75,000, then report GST on your BAS — usually quarterly.

• A$500 + GST = A$550 (A$50 GST); A$550 ÷ 11 = A$50 GST

• Registration threshold: A$75,000, or A$150,000 for non-profits; taxi and ride-sourcing drivers from the first dollar

• Tax invoice on request within 28 days for sales over A$82.50

• Quarterly BAS due 28 Oct, 28 Feb, 28 Apr and 28 Jul

What GST is and how much it is in 2026

The goods and services tax is a broad-based tax of 10% on most goods, services and other items sold or consumed in Australia. It has been the same rate since GST began on 1 July 2000.

GST is collected in stages. Each GST-registered business adds GST to its taxable sales and claims back — as GST credits — the GST included in its business purchases. It pays the ATO the difference. The end consumer, who can't claim credits, carries the tax.

That's why the maths matters on both sides of the ledger: you owe GST on what you sell and you recover GST on what you buy, as long as you hold the right paperwork.

How to calculate GST: the three formulas

Every GST calculation in Australia is one of these:

Why you divide by 11, not take 10% off

A GST-inclusive price is 110% of the base price. The GST is 10 parts out of 110 — one-eleventh. Taking 10% off the total gives the wrong answer:

• Wrong: A$275 × 10% = A$27.50 GST, leaving A$247.50.
• Right: A$275 ÷ 11 = A$25 GST, leaving A$250.

On a single sale the gap is small. Across a quarter of sales it can throw your BAS out by hundreds of dollars.

Rounding

GST is calculated to the cent. Where there's a fraction of a cent on an invoice with one taxable item, round to the nearest cent, rounding half a cent up. Invoices with several taxable items can use the ATO's total invoice rule (total the GST, then round) or the taxable supply rule (round each line). Pick one method and use it consistently.

Try it — find the GST inside A$1,320

Add TaxRemove Tax

AmountTax Rate

10% (GST)0% (GST-free)

Net Amount (Before Tax)$1,200.00

Tax (10%)$120.00

Gross Amount (Including Tax)$1,320.00

Open the full GST Calculator (PDF, save, compare)

The calculator above shows A$1,320 ÷ 11 = A$120 GST and A$1,200 before GST. Switch to Add Tax to go the other way.

Worked examples in Australian dollars

1. Pricing a service

Mia, a Brisbane photographer, wants A$1,800 for a wedding package before GST. She's registered, so she quotes A$1,800 × 1.1 = A$1,980. Of that, A$180 is GST she'll report on her BAS.

2. Checking a supplier's bill

A Perth café receives a bill for A$3,410 including GST for a coffee machine service. GST = A$3,410 ÷ 11 = A$310, so the service itself costs A$3,100. The café claims A$310 as a GST credit — provided it holds a valid tax invoice.

3. A mixed shopping basket

A corner store sells a loaf of bread (GST-free, A$5.00), a bottle of soft drink (taxable, A$4.40) and a magazine (taxable, A$11.00) to one customer:

• GST-free items: A$5.00 — no GST.
• Taxable items: A$4.40 + A$11.00 = A$15.40, of which GST is A$15.40 ÷ 11 = A$1.40.
• Total paid: A$20.40, including A$1.40 GST.

The receipt must make clear which items are taxable — a common marker is an asterisk with "includes GST".

Who must register for GST

You must register for GST:

• when your GST turnover — gross business income, not profit, minus GST — reaches A$75,000 or more, now or projected for the next 12 months;
• when you start a business that you expect to reach A$75,000 in its first year;
• when a non-profit reaches A$150,000;
• if you provide taxi, limousine or ride-sourcing travel, whatever your turnover;
• if you earn through the sharing economy or digital platforms such as food delivery, under the ATO's sharing-economy rules;
• if you want to claim fuel tax credits.

Otherwise registration is optional. If you register voluntarily, you generally stay registered for at least 12 months. You need an ABN first; then register through Online services for business, by phone, or through a registered tax or BAS agent.

The 21-day rule. Check your turnover each month. Once you reach or expect to reach the threshold, you have 21 days to register. Miss it and the ATO can make you pay GST on sales since the date you should have registered — even if you never charged it — plus penalties and interest. Backdating is limited to 4 years, except for fraud or evasion.

Example: Jack, a Hobart carpenter, invoiced A$61,000 in the past 11 months and has signed a A$20,000 job for next month. His projected turnover passes A$75,000, so he must register within 21 days of realising that — and charge GST on the A$20,000 job if registered by then.

Taxable, GST-free and input-taxed sales

If you're registered, everything you sell in Australia is a taxable sale unless it's GST-free or input-taxed.

Three kinds of sale under Australian GST

	Taxable	GST-free	Input-taxed
Add GST to the price?	Yes — 10%	No	No
Claim GST credits on related purchases?	Yes	Yes	No
Typical examples	Most goods and services, takeaway and restaurant food, tools, software, consulting	Most basic food, many medical and health services, some education and childcare, exports, sale of a business as a going concern	Residential rent, sale of existing residential premises, financial supplies such as lending
Effect on the business	GST passes to the customer	GST on inputs is refunded	GST on inputs becomes a cost

Add GST to the price?

Taxable

Yes — 10%

GST-free

No

Input-taxed

No

Claim GST credits on related purchases?

Taxable

Yes

GST-free

Yes

Input-taxed

No

Typical examples

Taxable

Most goods and services, takeaway and restaurant food, tools, software, consulting

GST-free

Most basic food, many medical and health services, some education and childcare, exports, sale of a business as a going concern

Input-taxed

Residential rent, sale of existing residential premises, financial supplies such as lending

Effect on the business

Taxable

GST passes to the customer

GST-free

GST on inputs is refunded

Input-taxed

GST on inputs becomes a cost

Common GST-free items

The ATO's list includes most basic food, some education courses and materials, some medical, health and care services and aids, some medicines, some childcare, water and sewerage, international transport, precious metals, duty-free sales, exports and farmland, among others. "Basic food" has detailed rules — fresh bread and vegetables are GST-free; hot food, soft drinks, confectionery and restaurant meals are taxable. Check the ATO's detailed food list for anything borderline.

Exports of goods are GST-free if the goods leave Australia within 60 days of the earlier of payment or invoice. Services supplied to a recipient outside Australia are usually GST-free too, under specific rules.

Why input-taxed is different

A landlord renting out a residential flat for A$2,500 a month doesn't charge GST. If she pays a plumber A$660 including GST, she can't claim the A$60 back — her costs rise by the GST she pays. A GST-free business, like a physiotherapist, also charges no GST but can claim the GST on its equipment and rent.

Tax invoices: the A$82.50 and A$1,000 rules

You need a valid tax invoice to claim GST credits on purchases over A$82.50, and you must give one to a customer who asks for it within 28 days — unless the sale is A$82.50 or less including GST.

What every tax invoice under A$1,000 must show

0/8

• That it is intended to be a tax invoice (e.g. the words 'Tax invoice')
• Seller's identity (name or business name)
• Seller's ABN
• Date of issue
• Brief description of what was sold, with quantity and price
• The GST amount — or 'Total price includes GST' if GST is exactly one-eleventh
• The extent to which each item is taxable
• From A$1,000: the buyer's identity or ABN as well

Share Print

Why A$82.50? It's A$75 plus A$7.50 GST — the point below which the ATO doesn't require a tax invoice. Invoices meeting the A$1,000-plus rules can be used for smaller sales too, so many businesses simply include the buyer's details every time.

Tax invoices can be paper, PDF or other digital formats. A Peppol eInvoice that follows the A-NZ specification and carries all mandatory data counts even without the words "tax invoice". Build a compliant one in minutes with our free invoice generator.

Reporting GST on your BAS

Once registered, you report GST on a business activity statement. Your cycle depends on GST turnover:

Worked quarterly BAS (Simpler BAS)

A small Melbourne grocery reports July–September:

Simpler BAS — July to September quarter

1. 1

   G1 Total sales: A$99,000

   All sales including GST — A$77,000 of taxable sales (GST-inclusive) plus A$22,000 of GST-free fresh food.

2. 2

   1A GST on sales: A$7,000

   Only taxable sales carry GST: A$77,000 ÷ 11 = A$7,000. GST-free sales add nothing to 1A.

3. 3

   1B GST on purchases: A$3,000

   Taxable purchases with tax invoices — rent, packaging, equipment, utilities — totalled A$33,000 including GST: A$33,000 ÷ 11 = A$3,000. GST-free stock bought from farmers carries no credit.

4. 4

   Net GST payable: A$4,000

   1A minus 1B = A$7,000 − A$3,000. If 1B were bigger, the ATO would refund the difference.

5. 5

   Lodge and pay by 28 October

   Lodge online or through an agent for possible extra time. Add PAYG withholding if you have staff.

   Tip: Set aside one-eleventh of each taxable sale in a separate account so the BAS bill is never a surprise.

If you employ staff, the same BAS carries your PAYG withholding — see our PAYG withholding guide.

Quarterly BAS is due on 28 October (July–September), 28 February (October–December, which already includes a one-month extension), 28 April (January–March) and 28 July (April–June). Monthly BAS is due on the 21st of the following month, and annual GST returns on 31 October.

If a due date falls on a weekend or public holiday, lodge and pay by the next business day. Lodging online may give an extra two weeks on quarters other than October–December. Late payment attracts the general interest charge; if you can't pay, the ATO offers online payment plans for debts of A$200,000 or less.

Cash or accrual GST accounting

Businesses with aggregated turnover under A$10 million can account for GST on a cash basis — you report GST on a sale when you're paid and claim credits when you pay. On the non-cash (accruals) basis you report when you invoice or are invoiced, whichever is first. Cash basis suits businesses that invoice on credit and wait for payment, because you don't pay GST before you've collected it.

Common GST mistakes

• Taking 10% off a GST-inclusive price. Always divide by 11 to find the GST inside a total.
• Charging GST before you're registered. You can't add GST or issue tax invoices until registered — and once required to register, you can't avoid it by not charging.
• Claiming credits without a tax invoice. For purchases over A$82.50, keep the invoice; bank statements alone aren't enough.
• Claiming GST on private use. Only the business share of a purchase is creditable.
• Treating input-taxed rent as GST-free. Residential landlords can't claim GST on repairs.
• Missing the threshold. Check projected turnover monthly — the 21 days clock starts when you know you'll pass A$75,000.

Official links

• ATO — How GST works
• ATO — Registering for GST
• ATO — Tax invoices
• ATO — GST-free sales
• ATO — Input-taxed sales
• ATO — Quarterly GST reporting and Simpler BAS
• ATO — BAS due dates
• business.gov.au — Register for GST

What to do next

If you're near A$75,000, get your ABN sorted and register for GST before the 21 days window closes. Set up your invoices to show GST correctly, keep every tax invoice for your purchases, and diarise your BAS dates. For quick checks, use our Australia GST calculator, and track margins after GST with the profit margin calculator.

This is general information, not legal or tax advice — confirm on the official source or with a professional.

Frequently asked questions

How do you calculate GST in Australia?

GST is 10% of the GST-exclusive price. To add GST, multiply the price by 1.1 — A$200 becomes A$220. To find the GST inside a GST-inclusive price, divide the total by 11 — A$220 ÷ 11 = A$20 GST. To get the price before GST, divide the total by 1.1. Round GST to the nearest cent, rounding half a cent up.

How much is GST in Australia in 2026?

GST in Australia is 10% on most goods, services and other items sold or consumed in Australia. The rate has not changed since GST started on 1 July 2000. Some sales are GST-free, such as most basic food, many medical and education services and exports, and others are input-taxed, such as residential rent and financial supplies.

When do I have to register for GST?

You must register within 21 days once your GST turnover reaches A$75,000 (current or projected), or A$150,000 for non-profits. Taxi and ride-sourcing drivers, sharing-economy platform workers and anyone claiming fuel tax credits must register regardless of turnover. You need an ABN first. Below the threshold, registration is optional.

Do I need to give a tax invoice for every sale?

No. A GST-registered seller must provide a tax invoice within 28 days if the customer asks, unless the sale is A$82.50 or less including GST. For sales under A$1,000 the invoice needs seven details, including your ABN and the GST amount; from A$1,000 it must also show the buyer's identity or ABN.

What is the difference between GST-free and input-taxed?

Both mean you don't add GST to the price. With GST-free sales — basic food, exports, many health and education services — you can still claim GST credits on the purchases you used to make them. With input-taxed sales — residential rent, sales of existing homes, financial supplies — you can't claim those credits, so the GST you paid on inputs becomes a cost.

When is my quarterly BAS due?

Quarterly BAS is due on 28 October (July–September), 28 February (October–December), 28 April (January–March) and 28 July (April–June). Lodging online or through a registered tax or BAS agent can give extra time on some quarters. Monthly BAS is due on the 21st of the following month, and annual GST returns for voluntary registrants are due 31 October.

Sources & verification

Figures on this page were checked against the sources below when it was last reviewed on 7 October 2026. Each rate and limit is stored once with its own official source and review date, and official update channels are monitored daily so changes are picked up. How we verify

1. 1.How GST works — Australian Taxation Office · accessed 7 October 2026
2. 2.Registering for GST — Australian Taxation Office · accessed 7 October 2026
3. 3.Tax invoices — Australian Taxation Office · accessed 7 October 2026
4. 4.GST-free sales — Australian Taxation Office · accessed 7 October 2026
5. 5.Input-taxed sales — Australian Taxation Office · accessed 7 October 2026
6. 6.When and how to report and pay GST — Australian Taxation Office · accessed 7 October 2026
7. 7.Quarterly GST reporting — Australian Taxation Office · accessed 7 October 2026
8. 8.Due dates for lodging and paying your BAS — Australian Taxation Office · accessed 7 October 2026
9. 9.Register for goods and services tax (GST) — business.gov.au · accessed 7 October 2026