GST Registration in Australia: The $75,000 Threshold and the 21-Day Rule
When does the $75,000 GST registration threshold apply in Australia? The 21-day rule, ATO penalties for late registration, and when voluntary registration makes sense.
By Timothy Hirou GaschereauPublished 9 min read
This article is general information only and does not constitute tax advice. This is part of a wider guide to crypto and alternative income on Snowball Invest.
Quick answer
You must register for GST once your GST turnover hits $75,000 (or $150,000 for non-profits), checked every month, not just at year end. You have 21 days to register from when you know, or reasonably should know, you've hit the threshold. Miss it and the ATO can hit you with a penalty plus backdated GST on every taxable sale, but registering before the ATO contacts you can get the penalty wiped or significantly reduced.
In this guide
- →What the $75,000 threshold actually is, and who must register regardless
- →How GST turnover is calculated, two rolling 12-month tests
- →The 21-day legal deadline once you hit the threshold
- →What happens, and what it costs, if you register late
- →When voluntary registration below the threshold makes sense
📊 What is the $75,000 threshold?
The GST registration threshold is $75,000 in GST turnover for most businesses, $150,000 for non-profits. Two types of businesses must register regardless of turnover: taxi, limousine and ride-sourcing operators, before their first trip, and fuel tax credit claimants, as soon as they want to claim. None of this applies until your activity actually counts as a business in the ATO's eyes, worth confirming that first if you're not sure.
🧮 How GST turnover is actually calculated
"GST turnover" is gross business income, not profit. Start with total gross income, then subtract GST already included in prices, input-taxed sales, and sales not connected with an enterprise you run or with Australia.
| Test | What it covers |
|---|---|
| Current GST turnover | This month plus the previous 11 months |
| Projected GST turnover | This month plus the next 11 months |
🎯 The essential: Even if your current GST turnover is at or above $75,000, you don't have to register if your projected turnover will stay below the threshold. Both tests matter, and you need to run them monthly if you're not yet registered.
⏳ The 21-day rule
Once you know, or reasonably should know, that either test hits $75,000, you have 21 days to register. The clock starts the moment you identify the threshold is reached or will be reached, not at the end of the financial year. Register online via ATO Online Services for Business, by phone on 13 28 66, or through a registered tax or BAS agent. You'll need an ABN first.
⚠️ What happens if you register late
Failing to register when required is a 20 penalty unit fine, currently in the thousands of dollars and rising over time as penalty unit values are periodically indexed, check the ATO's current penalty unit schedule for the exact figure. On top of that, the ATO can require you to pay GST on every taxable sale made from the date you should have registered, even if you never charged customers GST, coming straight out of your margin, and it can apply the General Interest Charge on unpaid amounts, which compounds daily and is no longer tax-deductible. Backdating is generally capped at 4 years unless fraud or evasion is involved.
If you self-register before the ATO contacts you, the penalty is often significantly reduced or remitted in full under the ATO's own remission guidance. You'll still owe the backdated GST and interest, but acting first limits the damage. If you've missed the deadline, register now, not later.
🙋 Voluntary registration below $75,000
Any business can register voluntarily. It tends to make sense if you have significant GST-inclusive business expenses, since registering lets you claim input tax credits back, or if your clients are mostly other businesses who can claim back the GST you charge them, so it doesn't cost them anything extra. Registering early is also worth it if you're planning to grow past $75,000 soon, your systems and processes are already set up when you hit the mandatory threshold.
The trade-off: you must charge GST on all your sales, not pick and choose, and you need to lodge a BAS regularly. If your clients are mostly consumers who can't claim GST back, or your expenses are low, the admin overhead may not be worth it.
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❓ Frequently asked questions
Do I check the $75,000 threshold at the end of the financial year?
+
No. You need to check your GST turnover every month if you're not yet registered. The threshold can be triggered at any point during the year, the financial year end is irrelevant.
What counts as "GST turnover"? Is it my profit?
+
No, it's your gross business income, not profit. You subtract GST already included in prices, input-taxed sales, and sales not connected with your enterprise or with Australia.
I hit $75,000 in current turnover but my projected turnover will drop below that. Do I still need to register?
+
No, if your projected GST turnover (this month plus the next 11 months) will stay below $75,000, you're not required to register, even if current turnover already crossed the line. Keep monitoring monthly.
I missed the 21-day deadline. What should I do?
+
Register immediately online or by calling the ATO. Self-registering before the ATO contacts you generally leads to a meaningfully reduced penalty, and often a full remission, compared to waiting to be caught. You'll still owe backdated GST and interest either way.
Can the ATO make me pay GST on sales where I never charged the customer?
+
Yes. If you were required to be registered and weren't, the ATO can assess GST on your taxable sales from the date registration was required, even if you didn't add GST to your invoices. That GST comes out of your margin.
Is voluntary registration worth it if I'm under $75,000?
+
It depends. If you have substantial GST-inclusive business expenses and mostly business clients, voluntary registration often pays for itself through input tax credits. If your clients are consumers and expenses are low, the admin overhead may outweigh the benefit.
📚 Recommended reading
The Barefoot Investor
Scott Pape
Australia's best-selling money book ever. A simple system for accounts, budgeting, debt and a real emergency fund in one.
Some links above are affiliate links. If you buy through them, Snowball Invest may earn a small commission at no extra cost to you. We only recommend books we'd suggest anyway.
Sources
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Timothy Hirou Gaschereau
Founder of Snowball Invest, not a financial adviser.
I write about what I'm learning myself, because nobody ever taught us how to take control of our own money. It's a skill, not a mystery, and it's never too late to learn it. The best day to start was yesterday, the second best is today.
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