An ABN and an ACN look almost identical and sound like the same thing, but they do different jobs, and not every business needs both. Mixing them up is one of the most common things we get asked about, so here is the plain-English version.
The short answer up front: an ABN identifies your business to the ATO and the wider public, and nearly every business needs one. An ACN identifies a company specifically, and you only have one if you have set up a company. Sole traders and partnerships have an ABN but no ACN.
An Australian Business Number (ABN) is an 11-digit number that identifies your business to the government, your customers and your suppliers. It is issued by the Australian Taxation Office through the Australian Business Register, and it is free to apply for.
You use your ABN on your invoices, when you register for GST, and when you deal with other businesses. Without one, other businesses may have to withhold 47% of any payment they make to you, so it matters even if you are only doing a bit of work on the side.
An ABN is not tied to being a company. A sole trader, a partnership, a trust and a company can all have one. It is about carrying on a business, not about your structure. If you are just setting up a business, the ABN is usually the first number you get.
An Australian Company Number (ACN) is a 9-digit number issued by the Australian Securities and Investments Commission (ASIC) when you register a company. It exists because a company is a separate legal entity, and ASIC needs a way to identify and track it.
You only have an ACN if you have actually set up a company. If you trade as a sole trader or a partnership, you will never have one. The ACN has to appear on certain company documents, and the company has to keep its details current with ASIC and pay an annual review fee each year to stay registered.
Here is the part that trips people up. When you register a company, you get the ACN first from ASIC. Then the company applies for its own ABN, and that ABN is simply the 9-digit ACN with two extra digits added to the front. So a company ends up with both numbers, and they are linked.
That is why you sometimes see an 11-digit ABN with a 9-digit ACN sitting inside it. It is the same entity, just two numbers for two different purposes: the ACN for company registration with ASIC, and the ABN for tax and everyday business dealings.
Not sure whether you need a company at all, or just an ABN as a sole trader? That is exactly the kind of thing we sort out on a quick call. Book a free call and we will point you in the right direction, with fixed fees agreed upfront and no jargon.
For most sole traders and tradies, the answer is simple: you need an ABN and that is it. You register for an ABN, you put it on your invoices, and if your turnover reaches the $75,000 GST threshold you also register for GST. No company, no ACN, less paperwork.
You only need an ACN if you decide to operate through a company. People usually do that to limit personal liability, or because the tax outcome suits them better as they grow. Whether it is worth it depends on your situation, and we have written a full breakdown of going with a sole trader or a company if you want to weigh it up.
The trap to avoid is registering a company because it sounds more official, then discovering the extra cost and admin that comes with it: annual ASIC fees, director obligations, separate company tax returns and stricter record-keeping. A company is a genuinely good move for a lot of businesses, but it is a decision to make on purpose, not by accident.
"Do I need an ABN and an ACN?" Only if you are a company. Sole traders just need the ABN.
"Is my ACN my ABN?" No, but your company's ABN is built from your ACN, so they share those 9 digits.
"Someone asked for my ACN but I am a sole trader." You do not have one, and that is fine. Give them your ABN instead.
"Do I pay for an ABN?" No. Applying through the Australian Business Register is free. If a website is charging you a fee just for the ABN itself, you are paying for their form, not the number.
One more thing worth knowing: an ACN stays with the company for its whole life, and if you ever wind the company up you have to formally deregister it with ASIC. We cover that in our guide on closing or deregistering a business, because leaving a company sitting there unused still racks up annual fees.
An ABN identifies your business for tax and trading, and almost everyone in business needs one. An ACN identifies a company specifically, and you only have one if you have set one up. If you are a sole trader, the ABN is your number and you can stop worrying about the ACN entirely.
If you are starting out and want to get the structure right the first time, we can help. Book your free call with Artiq Advisory. Every question answered within 24 hours, and fixed fees agreed before we start.
This article is general information only and does not take your personal circumstances into account. Please get advice tailored to your situation before acting.
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