How to invoice in Australia with an ABN: GST-registered or not
A plain-English guide to invoicing with an ABN in Australia: when to add GST, what changes on the invoice, and how to decide if registering early is worth it.
Every business operating in Australia needs an Australian Business Number on its invoices, whether you're a sole trader, a partnership, or running things through a company. GST registration is the separate decision layered on top of that — and it's the one that actually changes what your invoice has to say. Get the two mixed up and you'll either add a GST line you have no right to charge, or leave one off when a client's accounts team is expecting it.
This is written for anyone invoicing in Australia, but it leans toward sole traders and small operators making the GST call for the first time.
ABN first: the one thing you can't skip
An ABN isn't optional in the way GST registration is. If you invoice an Australian business without one, that business is required by law to withhold tax from what they pay you — as a rule of thumb, around 47%, taken off anything over $75 (excluding GST), unless a specific exemption applies. Most businesses know this rule, so they'll simply ask for your ABN before paying, or withhold if you don't supply it.
Applying for one is free and usually takes minutes through the Australian Business Register. Once you have it, put it on every invoice near your name — it's the first thing a client's accounts system checks for.
An ABN by itself doesn't mean you charge GST. It just means you're identifiable as a business. GST is a second, separate switch.
Do you need to register for GST?
This depends on turnover, and the exact threshold can move over time, so treat the figure below as a starting point and confirm the current number with your accountant or on the ATO website before deciding. As a rule of thumb, once your turnover looks likely to reach or pass roughly $75,000 in a 12-month period, GST registration becomes compulsory. Below that line, it's your choice.
Plenty of small operators register voluntarily before they hit the threshold, usually because it lets them claim GST credits back on tools, stock, or a work vehicle. The trade-off is that voluntary registration also means charging GST on everything you invoice from that point on, and lodging a Business Activity Statement — so it's worth the sums actually working in your favour before you opt in.
What changes on the invoice, either way
Not GST registered:
- No GST number, no GST line, no GST rate anywhere on the document.
- Call it a plain "Invoice," not a "Tax Invoice" — using the wrong label can make a client's bookkeeper assume you've charged GST when you haven't.
- Everything else is standard: your name or business name and ABN, a sequential invoice number, the date, a clear description of the work, the price, and your payment details.
GST registered:
- The document can be titled "Tax Invoice."
- Your ABN sits alongside your name as before.
- GST-inclusive total under $1,000: a simplified tax invoice is enough — your identity and ABN, the date, a description, and the GST-inclusive total.
- $1,000 or more: the ATO also expects the buyer's identity, and the GST amount shown separately from the price (or a clear statement that the total already includes GST).
In practice, most invoicing software — ours included — always shows the full GST breakdown regardless of the amount, since there's no real downside to including more detail than the legal minimum requires.
Telling a client you're not registered (yet)
If a client asks why there's no GST on your invoice, it's completely normal to just say you're not GST registered — no further explanation needed. Plenty of small sole traders operate below the threshold for years. What matters is consistency: don't add GST "just this once" for a bigger job and leave it off the rest of the time. Either you're registered or you're not, and the invoice should reflect whichever is actually true at the time you issue it.
A quick way to think about the decision
If most of your income comes from GST-registered business clients, voluntary early registration is often close to a wash for them — they claim the GST back anyway — while you gain the ability to claim GST credits on your own expenses. If most of your clients are individuals or GST-exempt, registering early effectively adds 10% to your price in their eyes, since they can't claim it back. There's no universal right answer here; it genuinely depends on who pays your invoices, and it's worth running the actual numbers with your accountant rather than guessing.
Keeping the paperwork straight once you decide
Whichever path you're on, a few habits make everything downstream easier:
- Use one sequential numbering format (INV-0001, INV-0002…) for the life of the business, with nothing skipped or reused. If you need to cancel an invoice, issue a credit note against it rather than deleting it.
- Put a real due date on every invoice ("Due 10 November 2026"), not "net 14" — people respond to calendar dates far more reliably than to arithmetic.
- If you register for GST partway through the year, make sure every invoice from that date forward reflects it correctly, and that older unpaid invoices aren't accidentally reissued with GST added after the fact.
- If you're GST registered, keep your BAS lodgement dates on your calendar — quarterly for most small businesses — and reconcile your invoices as you go rather than the week it's due.
The ATO generally expects invoices and related business records to be kept for five years, though the exact period can depend on your structure and circumstances, so it's worth confirming with your accountant rather than assuming.
Letting the software handle the switch
Manually tracking whether you're registered, which invoice format applies, and whether the $1,000 threshold kicks in is the kind of detail that's easy to get subtly wrong in a spreadsheet — especially in the months right around a GST registration change. InvoiceCharlie handles the formatting automatically: flip GST on in your settings and every invoice from that point switches to the correct layout, with sequential numbering and the right thresholds applied without you having to remember the rules each time.
If you just need to send one invoice today, the free invoice generator builds a correctly formatted ABN invoice — GST or not — with no account needed. And when you're ready for ongoing numbering, reminders and online payment handled for you, your first 10 invoices are free.