You must register for GST in Australia within 21 days of your GST turnover reaching $75,000 (or $150,000 for a non-profit). That test is your gross business income, not profit, measured over the current month plus the previous 11 months, or the current month plus the next 11. Taxi and ride-sourcing drivers, and anyone claiming fuel tax credits, must register regardless of turnover. Below the threshold, registering is optional.
That's the short answer. The longer answer is where most small business owners get caught: working out what actually counts towards the $75,000, noticing when you've crossed it, and knowing what changes in your books the day you register. Let's walk through it in plain English.
What is the GST registration threshold?
The GST registration threshold is the GST turnover figure at which registering for GST stops being optional. For businesses and other enterprises it's $75,000. For non-profit organisations it's $150,000.
Once you hit it, the ATO's registering for GST page is clear: you need to register within 21 days. You also need an Australian business number (ABN) before you can register, and you only register once, even if you run more than one business.
Quick definition: GST turnover. Your total business income (not your profit), minus the GST included in your sales, input-taxed sales, sales to associates that aren't for payment and aren't taxable, sales not connected with your enterprise, and sales not connected with Australia.
Who has to register for GST no matter what they earn?
The ATO lists a few situations where you must register even if you're nowhere near $75,000:
- Taxi, limousine and ride-sourcing drivers. If you provide passenger travel for a fare, including through a ride-sourcing app, you must register regardless of your GST turnover. This applies to owner-drivers and to drivers who lease or rent a vehicle.
- New businesses expecting to hit the threshold. If you start a business and expect turnover to reach $75,000 in the first year, you register from the start, not after you've proven it.
- Businesses claiming fuel tax credits. You must be registered for GST to claim them. We covered this in our fuel tax credits on your BAS guide.
- Some sharing economy and digital platform income. The ATO flags platform-based work as an area to check. If that's you, read the ATO's sharing economy guidance or ask us to look at your situation.
If none of these apply and your GST turnover is under the threshold, registering is your choice.
How do you work out your GST turnover?
This is the part people get wrong, usually because they look at last financial year's tax return and assume they're fine. The ATO uses two rolling tests, and you reach the threshold if either one hits $75,000:
- Current GST turnover: your turnover for this month plus the previous 11 months.
- Projected GST turnover: your turnover for this month plus what you reasonably expect over the next 11 months.
Because both are rolling 12-month windows, they move every month. The ATO's advice is to check each month if you're not registered.
What counts and what doesn't
Your GST turnover is built from your gross business income. A few things trip people up:
- It's income, not profit. A tradie who invoices $80,000 but spends $40,000 on materials has crossed the threshold. Expenses don't reduce GST turnover.
- Every business counts together. If you run a cleaning business and a side online store under the same ABN or entity, both feed the same GST turnover figure.
- Selling a business asset is left out of your projected turnover. Selling your old ute or a piece of equipment doesn't push your projection over the line.
- Winding down is left out too. Sales you make only because you're closing the business, or permanently scaling it right back, aren't counted in your projection.
- GST groups combine. If you're in a GST group, your turnover includes the other members' turnover but excludes sales between group members.
A quick example
Say Mia is a sole trader photographer. At the end of March, her income for March plus the previous 11 months is $68,000, so her current GST turnover is under the threshold. But she's just booked a run of wedding season work, and her income for March plus the next 11 months looks like it'll land around $82,000.
Her projected GST turnover reaches $75,000, so she's now required to register and has 21 days to do it. Waiting until her current turnover catches up would leave her registering late.
What happens if you register late?
If you were required to register and didn't, the ATO says you may have to pay GST on sales made since the date you should have been registered. That can apply even if you never charged GST to your customers. In practice, that means the GST comes out of money you've already earned and spent. You may also face penalties and interest.
Registration can be backdated, generally for up to 4 years unless there's fraud or evasion, and you need to phone the ATO's business enquiries line to request it.
If you've realised you crossed the threshold a while ago, don't panic and don't ignore it. The fix is to work out the date you were required to register, rebuild your sales figures from that date, and get your BAS position sorted. That's exactly the kind of catch-up work we do, with no judgement. Our catch-up bookkeeping guide explains how we approach it.
Should you register for GST voluntarily under $75,000?
Sometimes it makes sense, sometimes it doesn't. It depends on who your customers are and what you spend.
Registering voluntarily can suit you if:
- Most of your customers are GST-registered businesses. They can claim back the GST you charge, so adding 10% usually doesn't hurt your pricing.
- You have big start-up or ongoing costs with GST in them. Once registered, you can generally claim GST credits on business purchases like tools, equipment, software and fit-outs.
- You want to look established. Some larger clients prefer dealing with GST-registered suppliers.
- You need it for fuel tax credits. As above, registration is a requirement.
Staying unregistered can suit you if:
- You mainly sell to the public. Everyday consumers can't claim GST back, so you'd either raise prices by 10% or absorb it out of your margin.
- Your costs are low. If you don't buy much with GST in it, there are fewer credits to offset what you'd collect.
- You'd rather keep admin light for now. Registration means lodging activity statements and keeping your GST coding clean.
One thing to know before you decide: the ATO says that if you choose to register, you generally have to stay registered for at least 12 months. So it's not something to switch on for one big job and switch off the next month.
If you're weighing GST registration up alongside bigger questions, like changing your business structure or how it affects your income tax, that part is for your tax agent or accountant. We'll happily give them clean numbers to work from.
Not sure which side of the line you're on? As a registered BAS agent, we can check your rolling GST turnover from your bank feeds or Xero file and tell you where you stand. Get a free quote or call us on 0404 877 436.
What changes once you're registered for GST?
Registering isn't just a box you tick with the ATO. It changes how you price, invoice and keep your books from your effective date of registration.
1. Your prices and invoices
If you're registered, most of your sales become taxable sales, and you include 10% GST in the price unless the item is GST-free or input-taxed. When a GST-registered customer asks for a tax invoice, you must give them one within 28 days (unless the sale is $82.50 or less including GST).
The ATO's tax invoice rules say an invoice under $1,000 needs to show it's a tax invoice, your identity, your ABN, the date, what you sold with quantity and price, the GST amount (or "Total price includes GST" if GST is exactly one-eleventh), and which items are taxable. Sales of $1,000 or more must also show the buyer's identity or ABN.
Before you're registered, don't show GST on your invoices. Charging GST when you're not registered creates a mess that's no fun to unwind.
2. Your BAS and reporting cycle
Once registered, you'll lodge a business activity statement. According to the ATO's when and how to report and pay GST page, most small businesses report quarterly (GST turnover under $20 million). Businesses at $20 million or more report monthly.
If you're voluntarily registered with GST turnover under $75,000, you may be able to elect to report and pay GST annually. You need to check each year, as at 31 July, that you're still eligible. If your projected turnover reaches the threshold, you'll move back to quarterly or monthly reporting.
For quarterly lodgers, standard due dates are 28 October, 28 February, 28 April and 28 July. Lodging through a registered BAS agent can give you more time for some quarters. Our BAS due dates 2026–27 guide has the details.
3. Your bookkeeping and GST coding
This is where it gets real. Every sale and purchase from your registration date needs the right GST treatment in your software. In Xero, that means setting the correct tax rate on every invoice, bill and bank transaction, not just leaving the default and hoping.
Common slip-ups we see in the first few quarters after registration:
- Transactions dated before your registration took effect coded with GST. Those sales and purchases generally shouldn't be on your BAS, and your GST figures won't line up.
- Personal or private spending coded as a business purchase. That inflates your GST credits.
- GST-free or input-taxed items coded as taxable. Think most basic food, many medical items, or bank fees, none of which include GST.
- Missing tax invoices for purchases. To claim GST credits on larger purchases, you generally need a valid tax invoice from your supplier.
If you're on Xero, our walkthrough on how to prepare and lodge your BAS in Xero covers reconciling your GST before you lodge.
How to register for GST: step by step
- Get your ABN first. You can't register for GST without one.
- Work out your effective date. If you're registering because you've crossed the threshold, it's generally the date you were required to register, not the day you get around to it.
- Register. Do it through Online services for business, by phoning the ATO's business enquiries line, or through your registered tax agent or BAS agent.
- Wait for the ATO's confirmation. The ATO notifies you in writing of your GST registration details, including your effective date.
- Update your software. Turn on GST in Xero (or whatever you use), set your reporting basis and cycle, and check your tax rates.
- Update your invoice template and prices. Add "Tax invoice" and make sure your prices show whether GST is included.
- Diary your BAS dates. Or hand them to your BAS agent so they're not on your mental to-do list.
Can you cancel your GST registration?
Yes, if you're no longer required to be registered. For example, your turnover has dropped below the threshold, or you've stopped running the business. If you registered voluntarily, remember the general 12-month minimum. Cancelling has its own timing and BAS consequences, so it's worth a quick check with us or your tax agent before you do it.
Frequently asked questions
Is the $75,000 GST threshold based on profit or income?
Income. GST turnover is your gross business income minus GST and a few excluded items. Your expenses don't reduce it, so a business can cross the threshold while making very little profit.
How long do I have to register once I reach $75,000?
21 days. The ATO says you need to register within 21 days of your GST turnover reaching or exceeding the threshold, whether that's your current turnover or your projected turnover.
Do I use the financial year to work out my GST turnover?
No. The ATO uses rolling 12-month windows: this month plus the previous 11, or this month plus the next 11. Checking only at 30 June can mean you register months late.
I didn't register when I should have. What now?
Act sooner rather than later. You may owe GST on sales since your required registration date, plus possible penalties and interest. Registration can be backdated (generally up to 4 years). A BAS agent can rebuild your figures and get your activity statements up to date.
Do Uber and rideshare drivers need to register for GST?
Yes. If you provide taxi or ride-sourcing travel for passengers, you must register for GST regardless of your turnover, and the ATO expects you to be registered before you start.
Can I register for GST if I earn under $75,000?
Yes. Registration is optional under the threshold (unless one of the compulsory categories applies). If you choose to register, you generally need to stay registered for at least 12 months.
Can a bookkeeper register me for GST?
A registered BAS agent can advise on GST registration and lodge on your behalf. Girl Friday Australia is a registered BAS agent. For broader income tax or structure questions, speak to your tax agent or accountant.
The bottom line
The $75,000 GST threshold isn't hard to understand, but it's easy to miss. Watch your rolling turnover each month, register within 21 days once you hit it, and set your books up properly from the effective date. Getting those three things right saves you from paying GST out of your own pocket later.
If you'd like someone to keep an eye on your turnover, register you at the right time and handle your BAS from day one, that's what we do. We're a registered BAS agent and Xero Certified Advisor working with small businesses Australia-wide, with no lock-in contracts. BAS and IAS lodgement starts from $180 per quarter.
Book a free discovery call, get a free quote, call 0404 877 436 or email info@girlfridayaustralia.com. We reply within one business day.