How GST works in Australia
Australia's Goods and Services Tax (GST) is a flat 10% added to most goods and services. If your business is registered for GST, you add 10% on top of your prices, collect it from your customers, and pass it on to the ATO when you lodge your BAS. The GST you pay on your own business purchases (your "input tax credits") is subtracted, so you only hand over the net.
How to add GST to an amount
Times it by 1.1. A $500 job is $500 × 1.1 = $550, and $50 of that is GST. Adding GST is just 10% on top of your price, the calculator above does it as you type.
GST exclusive and GST inclusive
GST exclusive is the price before GST, GST inclusive is the price with the GST in it. Exclusive to inclusive, times by 1.1. Inclusive back to exclusive, divide by 1.1, and the GST inside an inclusive total is the total divided by 11. A $1,100 invoice has $1,100 ÷ 11 = $100 GST in it, leaving $1,000.
The divide by 11 catches a lot of people out. GST is 10% of the price before GST, so it’s only one eleventh of the total with GST in, about 9.09%, not 10% of it.
When the GST isn’t a whole cent
Plenty of prices give GST with half a cent in it. Add GST to $1.15 and it’s 11.5 cents. On one sale the ATO says “the amount of GST should be rounded to the nearest cent (rounding 0.5 cents upwards)”, so that’s 12 cents and $1.27 all up. The calculator rounds that way, and so does the free invoice generator. A lot of quick calculators drop the half cent and show 11.
Source: ATO, Tax invoices, last updated 18 September 2026, read 26 October 2026.
Do I need to register for GST?
As a sole trader, you must register for GST once your business turnover hits $75,000 in a 12-month period (current or expected). Under that, registering is optional. Some tradies register early so they can claim GST back on tools and a vehicle. Others hold off to keep their quotes 10% cheaper to homeowners.
Not sure whether a business is registered?
The register is public. Search it here, it’s handy for checking your own ABN, or a subbie's before you pay an invoice that has GST on it.
Two different questions, and the register only answers the first, is this ABN registered for GST (the register knows) and should I be registered (that depends on your turnover, see the $75,000 rule). A lookup never tells you what to do.
Quick reference
| You have… | You want… | Do this |
|---|---|---|
| Price before GST | Total with GST | × 1.1 |
| Total including GST | The GST portion | ÷ 11 |
| Total including GST | Price before GST | ÷ 1.1 |
Common amounts, plus GST
The ones people type straight into Google, done. Add 10%, and going backwards the GST inside any total is one eleventh of it.
| Before GST | Plus GST | GST in it |
|---|---|---|
| $50 | $55 | $5 |
| $100 | $110 | $10 |
| $150 | $165 | $15 |
| $250 | $275 | $25 |
| $350 | $385 | $35 |
| $500 | $550 | $50 |
| $1,000 | $1,100 | $100 |
| $1,500 | $1,650 | $150 |
What a valid tax invoice needs
Registered for GST and a customer asks for a tax invoice, you give them one within 28 days, unless the sale is $82.50 (including GST) or less. Every tax invoice shows it’s meant to be a tax invoice, your business name and ABN, the date, what you supplied with the quantity and price, the GST, and which items have GST on them. When the GST is exactly one eleventh of the total, a line saying “Total price includes GST” does instead of the figure. From $1,000 it also needs the buyer’s name or ABN. Getting this right is what lets your business customers claim their own GST back.
Source: ATO, Tax invoices, last updated 18 September 2026, read 26 October 2026.
See the GST on every job, as you go
One figure is easy. A quarter of them, split correctly between what you collected and what you paid, is the bit people leave until October.
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GST calculator FAQ
How much is GST in Australia?
GST is 10% on most goods and services. A handful of items (basic food, some health and education) are GST-free.
How do I take GST off a price?
Divide the GST-inclusive total by 11 to get the GST amount, or by 1.1 to get the price before GST. On a $550 total, the GST is $50 and the ex-GST price is $500.
Is GST 10% of the total?
No. GST is 10% of the price before GST, which works out to one eleventh (about 9.09%) of the GST inclusive total.
Do sole traders charge GST?
Only if you're registered for GST (required once turnover reaches $75,000). If you're not registered, you don't add GST and you don't issue tax invoices.
More free tools for tradies
This calculator and guide are general information for Australian businesses, not tax advice. GST rules and thresholds can change, check the ATO GST pages or your accountant for your situation.