ABN vs GST Registration — Do You Need Both in Australia?

An ABN and GST registration are two separate things, and having one doesn’t automatically give you the other. Your Australian Business Number identifies your business. GST registration is a separate step that only kicks in when your turnover hits $75,000 — or when you fall into a handful of special categories. You need an ABN before you can register for GST, but plenty of ABN holders never register for GST at all.

What Is an ABN?

An Australian Business Number is an 11-digit identifier issued by the Australian Business Register (ABR). It’s how the ATO, your customers, and other government agencies know who your business is. Every business structure — sole trader, partnership, company, or trust — can apply for one.

You don’t need to earn a minimum amount to get an ABN. You just need to be carrying on (or about to start) an enterprise in Australia. There’s no fee to apply through the ABR, and most applications are processed on the spot.

Without an ABN, any business or government agency that pays you must withhold 47% of the payment and send it to the ATO. That withholding rule alone is why almost every active business has one.

For a broader look at Australia’s GST system and how it connects to your business obligations, see our guide on what GST is and how it works in Australia.

What Is GST Registration?

GST registration is a separate step that tells the ATO your business will collect Goods and Services Tax — a flat 10% on most goods and services sold in Australia. Once registered, you charge GST on your taxable sales, lodge a Business Activity Statement (BAS), and can claim back GST credits on your business purchases.

Registration is tied to your ABN. The ATO uses your ABN as your GST registration number — there’s no separate GST number. But the two registrations are processed independently. Having an ABN doesn’t switch GST on. You either register during your ABN application or add it later.

For the full step-by-step process, head to our guide to registering for GST in Australia.

ABN vs GST Registration — The Differences That Matter

People mix these up all the time, and it’s easy to see why. Both involve the ATO. Both are tied to your business identity. But they serve completely different purposes.

Do You Need GST If You Already Have an ABN?

Not always. It depends on your turnover and what kind of work you do. Here’s how to figure it out.

The $75,000 threshold is based on gross income — your total business revenue before expenses, not your profit. And it’s calculated on a rolling 12-month basis, not just the financial year. So you need to check each month whether your current month plus the previous 11 months has crossed the line.

If you’re a sole trader trying to figure out where you stand, our post on sole trader GST registration walks through the decision in more detail.

Can You Have an ABN Without GST Registration?

Yes. This is actually the most common setup for small businesses and side hustles under $75,000 in annual revenue.

Here’s what you can do with an ABN alone (no GST registration):

• Invoice clients without the 47% no-ABN withholding penalty
• Open a business bank account
• Register a .com.au domain name
• Apply for government contracts (though some require GST registration separately)
• Operate your business without charging GST on sales

Here’s what you can’t do without GST registration:

• Charge GST on your invoices
• Issue tax invoices
• Claim GST credits (input tax credits) on business purchases
• Lodge a BAS

That last point — not claiming input tax credits — is why some businesses under $75,000 choose to register voluntarily. If you’re spending heavily on GST-inclusive supplies, those credits can add up. But voluntary registration also means you must stay registered for at least 12 months, charge GST on all your sales, and lodge BAS returns. It’s a trade-off.

To understand how input tax credits work, see our post on claiming GST back on business purchases.

The distinction also matters when an overseas platform asks for your ABN before deciding whether to charge Australian GST. See how this plays out for overseas subscriptions and digital services.

What Happens If You Don’t Register When You Should?

This is where it gets expensive. If your turnover passes $75,000 and you don’t register within 21 days, the ATO can:

A business earning $100,000 per year that should have been registered but wasn’t could owe roughly $9,091 in GST for that year alone ($100,000 ÷ 11). Add penalties and interest, and the bill climbs fast. That quirk — dividing by 11, not by 10 — catches a lot of people off guard. Our post on why you divide by 11 for GST explains the maths behind it.

How to Register for Both — ABN and GST Together

If you’re starting a new business and expect to hit the $75,000 threshold, the easiest path is to register for both at the same time. The ABN application on the Australian Business Register includes an option to add GST registration in the same form.

If you already have an ABN, you can add GST later through ATO Online Services for Business, by calling the ATO on 13 28 66, or through a registered tax agent or BAS agent.

Either way, there’s no fee. The ATO doesn’t charge for ABN or GST registration. You’ll need a myID (formerly myGovID) linked to your business via the Relationship Authorisation Manager (RAM) if you’re registering for a company, trust, or partnership.

Once you’re GST-registered, you’ll need to lodge BAS returns — usually quarterly for small businesses, monthly if your turnover is above $20 million. You’ll also need to use our GST calculator to make sure your pricing and invoicing are correct from day one.

Frequently Asked Questions

Is an ABN the same as a GST number in Australia?

No. Your ABN is your business identifier. If you register for GST, the ATO uses your ABN as your GST registration number — but they’re two separate registrations. Having an ABN doesn’t mean you’re registered for GST, and you won’t get a separate GST number when you register.

Can I register for GST without an ABN?

No. The ATO requires you to have an active ABN before you can register for GST. You can apply for both at the same time during the ABN application process, but the ABN must be issued first.

Do I need to register for GST if my turnover is under $75,000?

Generally, no. Registration is optional below $75,000 unless you drive a taxi, limo, or ride-sourcing vehicle, or you want to claim fuel tax credits. Some businesses under the threshold choose to register voluntarily so they can claim GST credits on their purchases.

What’s the penalty for not having an ABN when invoicing?

If you don’t quote an ABN on your invoice, the business paying you is required to withhold 47% of the payment and send it to the ATO. You can claim this back when you lodge your tax return, but it creates a serious cash flow gap in the meantime.

How do I check if a business is GST-registered?

Use the free ABN Lookup tool on the Australian Business Register website. Enter the business’s ABN and it’ll show whether they’re currently registered for GST, along with their registration date.

Can I cancel my GST registration if my turnover drops?

Yes. If your GST turnover falls below $75,000 and you expect it to stay there, you can apply to cancel through ATO Online Services, by phone, or through your tax agent. If you registered voluntarily, you must stay registered for at least 12 months before cancelling.

Do I charge GST if I only have an ABN but I’m not GST-registered?

No. You can’t charge GST, and you can’t issue tax invoices. Your invoices should clearly state that the total does not include GST. Charging GST when you’re not registered is a compliance breach.

I just started my business. Should I register for GST straight away?

Only if you expect your turnover to reach $75,000 in your first year, or if you’re in a mandatory category like ride-sourcing. Otherwise, registration is optional. Monitor your turnover monthly and register within 21 days if you cross (or expect to cross) the threshold.