How to Register for GST in Australia (and Whether You Should)

You must register for GST once your GST turnover reaches $75,000 in any rolling 12-month period, and you have 21 days from that point to do it (as at September 2026). Under $75,000, registering is optional, and whether you should comes down almost entirely to who your customers are. Here's how the threshold really works, how to register for free in about 10 minutes, the two choices the form will ask you to make, and how to backdate or cancel if things change.

Do you need to register for GST?

Registration is compulsory if any of these apply:

Your situation	Must you register?
GST turnover of $75,000 or more (rolling 12 months)	Yes, within 21 days
Not-for-profit with GST turnover of $150,000 or more	Yes, within 21 days
You drive a taxi, limousine or rideshare (Uber, DiDi and the like)	Yes, before your first fare, whatever you earn
You want to claim fuel tax credits	Yes, regardless of turnover
None of the above	No, registration is voluntary

Two things trip people up. First, it's turnover, not profit: a tradie invoicing $90,000 with $60,000 of materials and vehicle costs is well over the line. Second, it's a rolling 12-month window, not a financial-year test, so you can cross the threshold in March as easily as in June.

How GST turnover is worked out

The ATO runs two tests, and you must register if you fail either:

• Current GST turnover: actual sales for this month plus the previous 11 months.
• Projected GST turnover: reasonably expected sales for this month plus the next 11 months.

The projected test catches growing businesses. Land a $40,000 contract in your second month and you're expected to register now if $75,000 over the coming year is a reasonable expectation, not once the money lands.

Turnover includes all your taxable sales plus GST-free sales (exports, most basic food, most health and education services). It excludes input-taxed sales such as residential rent, sales of capital assets like your work van, private sales unrelated to the business, and the GST itself; turnover is always measured GST-exclusive.

If you're not registered, check your rolling 12-month figure every month. Your accounting software's sales report makes this a two-minute job.

The 21-day rule

Once either test says you've hit the threshold, you have 21 days to register, and your registration takes effect from the date you crossed the line, not the date you filled in the form. That's why it pays to register the moment you can see the threshold coming.

What happens if you don't register when you should

If you were required to be registered, you owe GST on every sale from that date, whether or not you added it to your prices. GST is one-eleventh of a GST-inclusive price, so a business that ran $30,000 over the threshold for a year owes roughly $2,700 it never collected, paid from its own pocket.

On top of the tax, the ATO can add failure-to-register and failure-to-lodge penalties (set in penalty units, worth $364 each from 1 July 2026), general interest charge that compounds daily, and shortfall penalties if it decides the omission was careless or deliberate.

The ATO says genuine mistakes are treated more gently when you come forward first. If you've just realised you should have registered months ago, talk to your accountant or a registered BAS agent about a backdated registration and voluntary disclosure before data-matching finds you.

Should you register voluntarily under $75,000?

This is the real decision, and it depends on who pays your invoices.

	Mostly business customers (B2B)	Mostly consumers (B2C)
Effect of adding 10% GST	None: registered customers claim it back	Prices rise 10%, or you absorb 1/11th of revenue
GST credits on your purchases	You get them	You get them
Perception	Registered looks established; procurement teams often expect it	Customers don't care
Admin	BAS every quarter (or annually)	BAS every quarter (or annually)
Usual answer	Register now	Wait until you have to

Three other situations tip the balance towards registering early:

• You're spending heavily on setup. GST credits on a $30,000 vehicle or fit-out (roughly $2,700) are only available if you're registered when you buy.
• You sell GST-free goods or services. Exporters and some health and food businesses charge no GST but still claim credits, so registering is nearly pure upside.
• You'll cross the threshold within a year anyway. Registering from the start avoids a mid-year price change and a messy partial year.

Against that, a consultant with a laptop and consumer clients has little GST to claim back and a 10% price problem, and voluntary registrations generally have to stay in place for at least 12 months. Rule of thumb: register early if more than half your revenue comes from GST-registered businesses or you're about to buy significant equipment; otherwise let the threshold decide.

How to register for GST (step by step)

You need an ABN first. If you haven't got one, our guide to registering an ABN for free covers it, and you can apply for the ABN and GST together in one sitting.

Method	Best for	Notes
ATO Online services for business	Existing ABN holders	Log in with your myID and add GST as a new registration
Business Registration Service (business.gov.au)	New businesses	Apply for ABN, GST, business name and PAYG withholding in one application
Phone the ATO on 13 28 66	Anyone who'd rather talk it through	Have your ABN and TFN handy
Your tax agent or BAS agent	Anyone already using one	Done through the agent's portal, usually as part of setup

Registration is free. If a website is charging you to "register for GST", it's a third-party service adding nothing the ATO doesn't provide at no cost. Go direct.

What the form will ask you

Beyond your ABN and contact details, decide these four things before you start:

1. Date of effect. If you're required to register, it's the date you crossed the threshold. If you're registering voluntarily, you choose: today, or a date up to four years back (see backdating below).
2. Expected GST turnover. Your best estimate for the next 12 months.
3. Accounting method. Cash or non-cash (accruals).
4. Reporting cycle. Monthly, quarterly or annually.

Simple online applications are typically approved immediately, and from your registration date you must charge GST, keep GST records and lodge every activity statement, even a nil one.

Choice 1: cash or accruals accounting

This decides when a sale or purchase lands on your BAS.

• Cash basis: you report GST in the period you actually receive payment or pay a supplier.
• Non-cash (accruals) basis: you report GST in the period you issue an invoice or receive a bill, paid or not.

You can choose either if your aggregated turnover is under $10 million (as at September 2026). Above that you use accruals unless the ATO agrees otherwise.

	Cash basis	Accruals basis
GST on a $5,500 invoice issued 25 June, paid 20 July	July–September quarter	April–June quarter
Cash flow	You never pay GST on money you haven't received	You can owe GST on unpaid invoices
Matches	Your bank account	Your profit and loss report
Suits	Most small businesses, especially services with slow payers	Businesses carrying stock, or wanting accounts and BAS to line up

For most small businesses, cash is the safer choice: your BAS bill always reflects money that has actually arrived. Set the same basis in your accounting software so its BAS report matches what you lodge. You can change later by telling the ATO, but only from the start of a tax period.

Choice 2: how often you report

Cycle	Who can use it	What it means
Quarterly	GST turnover under $20 million (the default)	Four BAS a year, due 28 October, 28 February, 28 April and 28 July, with extra time for online or agent lodgement
Monthly	Compulsory at $20 million or more; optional below	Twelve BAS a year; suits businesses that get regular GST refunds, such as exporters
Annually	Voluntarily registered and under $75,000 ($150,000 NFP)	One GST return a year, no GST payments during the year

Quarterly is right for almost everyone. Monthly only makes sense if you're consistently in a refund position, and annual reporting means a year's GST lands in one hit, so set it aside as you go. Every date and concession is in our BAS due dates for 2026–27.

Backdating a GST registration

You can ask the ATO to start your registration from an earlier date, either to fix a missed threshold properly or to claim GST credits on equipment bought before you registered.

The ATO can backdate up to four years (further only where there's fraud or evasion). You'll usually need to phone to request it, and once done you must lodge an activity statement for every period back to the new start date and pay GST on all sales in that window. If those sales were priced without GST, that comes out of your margin, so weigh the credits you'd gain against the GST you'd owe before backdating voluntarily.

Cancelling your GST registration

You can cancel if your GST turnover has dropped below $75,000 and you don't reasonably expect it to go back over the threshold in the next 12 months. Voluntary registrants generally need to have been registered for at least 12 months first.

You must cancel if you close or sell the business, or your structure changes (a sole trader moving to a company gets a new ABN and a new registration). The ATO expects this done promptly once you stop trading, along with cancelling your ABN within 28 days.

Cancel through Online services for business, by phone or via your agent. You'll nominate a cancellation date and must lodge a final BAS up to that date. If you keep business assets you claimed GST credits on, such as a vehicle, expect an adjustment in that final BAS that hands some of those credits back; ask your accountant to work it out first. And think twice before cancelling because one quiet year dipped you under $75,000: cross the line again within months and you're re-registering, possibly with backdating and penalties attached.

What changes once you're registered

Three things start on your registration date:

1. Your prices include GST. Add 10%, or accept that 1/11th of what you already charge now belongs to the ATO. Update quotes, website and price lists the same day.
2. Your invoices become tax invoices. For any sale over $82.50 including GST, a customer can request a tax invoice and you must provide it within 28 days, showing your ABN, the words "tax invoice" and the GST amount.
3. Every transaction needs a GST code. Our guide to GST-free vs BAS excluded vs input taxed explains which code goes where, and GST and BAS explained covers how the GST you collect turns into a lodgement.

Key takeaways

• Registration is compulsory at $75,000 of GST turnover in any rolling 12 months ($150,000 for not-for-profits), tested on both actual and projected sales, and you have 21 days to act.
• Taxi and rideshare drivers must register before their first fare, whatever they earn.
• Miss the deadline and you owe GST on every sale from the date you should have registered, plus possible penalties and interest.
• Under the threshold, register early if most customers are GST-registered businesses or you're about to buy significant equipment; otherwise wait.
• Registering is free and takes about 10 minutes online. Choose cash accounting and quarterly reporting unless you have a specific reason not to.
• Registrations can be backdated up to four years, and voluntary registrations generally lock you in for 12 months.

Where to get help

• ATO: Registering for GST at ato.gov.au covers the thresholds, turnover tests and registration options; the ATO business line is 13 28 66.
• Business Registration Service at business.gov.au for applying for an ABN, GST and other registrations in one go.
• ATO Online services for business to add GST to an existing ABN, change your reporting cycle or cancel.
• Your accountant or a registered BAS agent can register you, choose the method and cycle to suit your cash flow, and handle backdating or voluntary disclosure. Check they're on the Tax Practitioners Board register first.