Australia GST Calculator
Let Australian business owners, sole traders and consumers instantly add 10% GST to a price or back out the GST component from a GST-inclusive amount, showing the net amount, the GST portion and the total.
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Worked example
Example 1 - Adding GST. A tradesperson quotes a net price of $800 for a job and needs to add GST.
- GST = $800 x 0.10 = $80.00
- GST-inclusive total = $800 x 1.1 = $880.00
The customer pays $880, of which $80 is GST the business must remit to the ATO.
Example 2 - Removing GST. A supplier issues a tax invoice for a GST-inclusive total of $1,650. To find the GST already included:
- GST component = $1,650 / 11 = $150.00
- Net (GST-exclusive) amount = $1,650 / 1.1 = $1,500.00
If the business is registered for GST, it can claim the $150 as a GST credit on its BAS at label 1B.
How to add and remove 10% GST in Australia
Australia's goods and services tax (GST) is a flat 10% applied to most goods, services and other items sold or consumed in the country. Because the rate never changes, the maths is simple once you know which direction you are working in.
Adding GST to a net price
If you have a GST-exclusive (net) price and want the GST-inclusive total, multiply by 1.1. The GST itself is 10% of the net price:
- Net price x 1.1 = GST-inclusive total
- Net price x 0.10 = GST amount
So a $250 net price becomes $250 x 1.1 = $275, with $25 of GST.
Removing GST from a GST-inclusive price
This is where people trip up. When a price already includes 10% GST, the GST is not 10% of the total - it is one eleventh of it. The ATO states plainly that GST is 1/11th of the amount you charge on a taxable sale. To back it out:
- GST-inclusive total / 11 = GST amount
- GST-inclusive total / 1.1 = net (GST-exclusive) amount
For a $110 shelf price, the GST is $110 / 11 = $10, and the net amount is $100. Dividing by 11 (not 10) is the single most common GST calculation error, and it matters because the wrong figure flows straight through to your Business Activity Statement.
Why 1/11, not 10%?
A net amount of $100 plus 10% GST equals $110. The $10 of GST is 10% of the net figure but only 9.0909% of the $110 total - which is exactly 1/11. Whenever the amount in front of you already contains GST, use the divide-by-11 rule.
Who has to register for GST
Charging GST is not optional once your business crosses the registration threshold, and it is a choice below it. The key numbers from the ATO are:
- $75,000 - the GST turnover threshold for most businesses and sole traders. Once your current or projected annual GST turnover reaches this figure, you must register.
- $150,000 - the higher threshold for not-for-profit organisations.
- 21 days - you must register within 21 days of your GST turnover exceeding the relevant threshold.
- Any turnover - taxi, limousine and ride-sourcing (rideshare) drivers must register for GST regardless of how little they earn.
GST turnover means your gross business income minus any GST included in sales - it is not your profit. The ATO lets you test it two ways: your current GST turnover (this month plus the previous 11 months) and your projected GST turnover (this month plus the next 11 months). If either reaches $75,000 you generally need to register. If your current turnover is over the threshold but you can show your projected turnover for the year ahead will stay under it, you may not have to register.
Registering voluntarily
Businesses under $75,000 can still register by choice. The main benefit is being able to claim GST credits on the GST you pay for business purchases. The trade-off is that you must then charge GST on your sales, issue tax invoices, and lodge a BAS. For a business selling mainly to GST-registered customers, voluntary registration is often worthwhile; for one selling to the public on price, adding 10% can make you less competitive.
Once registered, you charge GST on taxable sales, claim credits on eligible purchases, and report the difference to the ATO. You keep registering with a single Australian Business Number (ABN).
GST, tax invoices and your BAS
Collecting GST is only half the job - you also have to report and pay it. Registered businesses do this through the Business Activity Statement (BAS), usually lodged quarterly, though some report monthly or annually depending on turnover and ATO requirements.
What goes on the BAS
The core GST figures on a BAS are:
- 1A - GST on sales: the GST you collected from customers. Using the calculation worksheet, you take your total GST-inclusive sales and divide by 11.
- 1B - GST on purchases: the GST credits you can claim, calculated by dividing your total GST-inclusive purchases by 11.
You pay the ATO the difference between 1A and 1B. If your credits exceed the GST you collected, you receive a refund. This is exactly why getting the divide-by-11 calculation right on every invoice matters - each line feeds these totals.
Tax invoices
To claim a GST credit for a purchase of more than $82.50 (GST-inclusive), you generally need a valid tax invoice from your supplier. A tax invoice must show the seller's identity and ABN, that GST is included, and enough detail to identify what was sold. For sales of $1,000 or more it must also show the buyer's identity or ABN.
Keeping the numbers clean
Because GST is 1/11 of a tax-inclusive figure, cents can round differently across many lines. Calculate GST per taxable sale, round to the nearest cent, and keep GST-free and input-taxed items (such as most basic food, some health and education, and residential rent) out of your taxable totals. Feeding accurate GST-inclusive figures into the divide-by-11 rule keeps your 1A and 1B labels correct and your BAS reconciled.
Frequently asked questions
What is the GST rate in Australia in 2025?
GST is a flat 10% on most goods and services sold or consumed in Australia. The rate has been 10% since GST was introduced in July 2000 and has not changed for 2025-26.
How do I calculate GST on a GST-inclusive price?
Divide the GST-inclusive total by 11 to get the GST amount. For example, $220 / 11 = $20 of GST, leaving a net price of $200. This works because 10% GST equals exactly 1/11 of a GST-inclusive price.
How do I add GST to a price?
Multiply the GST-exclusive (net) amount by 1.1. For example, $500 x 1.1 = $550, which includes $50 of GST (500 x 0.10).
When do I have to register for GST?
You must register once your GST turnover reaches $75,000 or more (or $150,000 for not-for-profits), and you have 21 days to do so after crossing the threshold. Taxi and rideshare drivers must register regardless of turnover.
Why do I divide by 11 instead of 10 to find GST?
Because the price already includes GST. A $100 net price plus 10% GST is $110, and the $10 of GST is 1/11 of that $110 total, not 10% of it. Dividing a GST-inclusive figure by 10 overstates the GST.
How do I report GST to the ATO?
Registered businesses report GST on a Business Activity Statement (BAS), usually quarterly. You show GST collected on sales at label 1A and GST credits on purchases at label 1B, then pay the difference to the ATO or receive a refund.