GST Claims: How to Check if Your Supplier is Registered

I had a client — a contractor — who'd been buying supplies from a mate. The mate had an ABN, the invoices looked professional with GST listed, so my client claimed the GST. It felt right. But when we audited his accounts before tax time, I checked the mate's ABN in the register. Not GST registered. That meant my client shouldn't have claimed the GST at all. Suddenly we had to write back $2,000 in tax claims.

The ATO noticed it in the audit. It got messy.

This is a really common mistake — not because business owners are careless, but because the signals feel confusing. If a supplier has an ABN and lists GST on their invoice, surely they're registered, right? Not necessarily. An ABN doesn't automatically mean GST registration.

The difference between an ABN and GST registration

Let me clarify this because it's important.

ABN (Australian Business Number): An ABN is a unique 11-digit identifier for any business operating in Australia. It's issued by the ATO and is required for most businesses. But ABN registration doesn't automatically mean you're registered for GST.

GST Registration: GST registration is separate. It's when a business registers to pay GST and claim input tax credits (the GST they've paid on purchases). GST registration is required if your turnover exceeds $75,000 per year. Below that threshold, GST registration is optional.

So here's the catch: a supplier can have an ABN and not be registered for GST. They might be operating below the $75,000 threshold, or they might have chosen not to register for other reasons (some industries like financial advice are GST-free). Either way, if they're not registered for GST, they can't charge you GST, and you can't claim it.

Why it matters for your BAS

When you submit your BAS quarterly, you declare the GST you've collected from customers (on sales) and the GST you've paid on purchases (input tax credits). If you've claimed GST on purchases from a supplier who isn't registered, you've overstated your input tax credits. That means you're claiming tax credits you're not entitled to.

The ATO can claw this back — and they will, especially if it becomes a pattern. They cross-reference supplier registrations with claim patterns. If you consistently claim GST from the same non-registered supplier, that's a red flag.

Plus, if you get it wrong, it affects your tax position. You might owe more GST (and hence more tax overall) than you thought.

How to check if a supplier is GST registered

The good news: it's free and easy. You can check in literally 30 seconds using the ABN Lookup tool.

Step 1: Go to the ABN Lookup website (abr.business.gov.au)

Step 2: Enter the supplier's ABN in the search box

Step 3: Look at the results. The ABN details will show the entity name, address, and — here's the key bit — their GST registration status. It will explicitly say whether they are or aren't registered for GST.

Step 4: If they're not registered, you can't claim the GST. If they are registered, you can claim it.

That's it. Takes 30 seconds, and it could save you thousands in tax problems.

What if you've already claimed GST you shouldn't have?

If you've made this mistake and already claimed GST from a non-registered supplier, here's what to do:

1. Catch it early if possible. Before you lodge your BAS, go back through your invoices and check supplier registrations. Amend your GST claims before you lodge.

2. Amend your BAS if you've already lodged. You can lodge an amended BAS going back two years. If you've overclaimed, it's better to amend it yourself than wait for the ATO to find it.

3. Document everything. Keep a record of which suppliers you checked and when, and which ones weren't registered. This shows good faith if the ATO ever questions it.

4. Fix it going forward. Once you know a supplier isn't registered, don't claim GST on their invoices anymore. Simple.

How to avoid this problem entirely

Here's what solid bookkeeping practice looks like:

• Check supplier GST status when you first work with them. Do an ABN lookup. Note their registration status in your system. I typically have a "supplier master file" that includes GST status.
• Tag invoices in your accounting software. Good accounting systems let you tag invoices as "GST-registered supplier" or "non-GST-registered." This prevents you from accidentally claiming GST on the wrong invoices.
• Review before BAS time. Before you submit your BAS, do a quick mental check: have any of my suppliers changed their GST status? Have I added new suppliers? Have I checked their registration?
• Work with a bookkeeper who knows the rules. This is honestly the easiest solution. A bookkeeper will automatically check supplier registrations and make sure only legitimate GST claims make it onto your BAS.

The bigger picture

GST compliance isn't complicated once you understand the rules. And one of the clearest rules is: you can only claim GST on purchases from GST-registered suppliers. A 30-second ABN lookup each time you onboard a new supplier removes the risk entirely.

This is the kind of detail-oriented bookkeeping that keeps you out of trouble with the ATO and makes sure your tax position is clean and defensible.

Common questions