ABN vs ACN: What's the Difference in Australia?
ABN or ACN? The plain-English difference: who needs which, how a company's ABN is built from its ACN, what each costs, and how to get them.
By Timothy Hirou GaschereauPublished 9 min read
ABN, ACN, TFN: Australian business has a lot of three-letter numbers, and the ABN and ACN get mixed up constantly. The short version is that almost every business has an ABN, but only companies have an ACN, and if you run a company the two are actually linked.
Here is the plain-English difference, who needs which, and how they connect.
🎯 The essential: An ABN (11 digits, from the ABR/ATO) can be held by any business structure: sole trader, partnership, company or trust. An ACN (9 digits, from ASIC) is issued only to registered companies. If you have a company you need both, and your ABN is simply your ACN with two check digits added to the front. Sole traders, partnerships and trusts have an ABN and no ACN. An ABN is free; getting an ACN means registering a company, which costs an ASIC fee and brings ongoing obligations. Neither is a TFN.
What is an ABN?
An Australian Business Number is an 11-digit identifier issued by the Australian Business Register (administered by the ATO), and any business structure can have one. You use it to issue tax invoices, register for GST, deal with the ATO, identify your business to others, and avoid the 47% no-ABN withholding rule (where a payer must withhold nearly half your payment if you cannot quote a valid ABN). It is publicly searchable on ABN Lookup, which is the point: it gives other businesses confidence you are legitimate. Importantly, an ABN is not a TFN: your TFN is private and must never go on an invoice.
What is an ACN?
An Australian Company Number is a 9-digit identifier issued by ASIC, and only when you register a company (a Pty Ltd or public company). That is the critical distinction: only companies get an ACN. If you are a sole trader, partnership or trust, you will never have one and do not need one. Once ASIC issues your ACN it must appear on all company documents (contracts, invoices, letterhead, website), a legal requirement under the Corporations Act, and it is searchable on ASIC Connect.
The crucial relationship: how they connect
This is where people get confused, so it is worth seeing clearly:
So a company must have both numbers: you cannot legally operate a company with just an ACN and no ABN. The ABN is what you use for tax, invoicing and GST; the ACN identifies the legal entity registered with ASIC. You can verify the link on any Pty Ltd: look it up on ABN Lookup, strip the first two digits from the ABN, and the ACN is sitting right there.
ABN vs ACN, side by side
| Feature | ABN | ACN |
|---|---|---|
| Issued by | ABR (via the ATO) | ASIC |
| Digits | 11 | 9 |
| Who has one | Any business structure | Companies only |
| Purpose | Tax, invoicing, GST | Identifies the company entity |
| Cost | Free | ASIC registration fee (~$611) |
| Public register | ABN Lookup | ASIC Connect |
Who needs which
- Sole trader: an ABN, no ACN. Apply free at abr.gov.au in about 15 minutes.
- Partnership: the partnership needs its own ABN, no ACN.
- Trust: the trust needs an ABN (the trustee applies), no ACN.
- Company (Pty Ltd): both. Register with ASIC first (ACN issued immediately), then get the ABN, or do both in the one ASIC session.
An ABN does not make you a company, and you do not need an ACN to run a business: the vast majority of small businesses in Australia operate as sole traders or partnerships with just an ABN, perfectly legally. Whether to register a company is a real decision with tax and liability implications, so see our sole trader vs company guide before you commit.
How to get each
An ABN is free at abr.gov.au: you need your TFN, business activity details and address, and you must be genuinely carrying on or starting an enterprise (hobbyists are generally not entitled). Most applications are instant. An ACN comes from registering a company with ASIC (around $611 in 2025-26, plus an ongoing annual review fee and a company tax return); ASIC issues the ACN immediately and you apply for the ABN in the same flow. One warning: applying for an ABN direct at abr.gov.au is free, so avoid third-party sites that charge a fee for it. If your existing ABN was cancelled, see how to reactivate a cancelled ABN.
Frequently asked questions
What is the difference between an ABN and an ACN?
+
An ABN (Australian Business Number) is an 11-digit identifier issued by the ABR/ATO that any business structure can hold. An ACN (Australian Company Number) is a 9-digit identifier issued by ASIC only to registered companies. An ABN is for tax and invoicing across all business types; an ACN identifies a company as a legal entity under the Corporations Act.
Does a sole trader need an ACN?
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No. Sole traders do not need, and cannot obtain, an ACN, because an ACN is only issued when you register a company with ASIC. As a sole trader, your ABN is all you need to identify your business.
Can I have an ABN without an ACN?
+
Yes. Most Australian businesses, including sole traders, partnerships and trusts, have an ABN but no ACN. An ACN only enters the picture when you register a company.
How do I get an ABN?
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Apply online for free at abr.gov.au. You need your TFN, your business activity details and your business address. Most applications are processed instantly, though some are referred for review and can take up to 28 days. Applying direct is free, so avoid third-party sites that charge a fee.
How do I get an ACN?
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You get an ACN by registering a company with ASIC at asic.gov.au, which issues the ACN immediately. The fee to register a proprietary company is around $611 (2025-26), and you can apply for the company's ABN in the same session. A company also takes on ongoing obligations, like an annual review fee and a company tax return.
Is an ABN the same as a TFN?
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No. An ABN is a public business identifier used on invoices and for tax dealings. A TFN (Tax File Number) is a private number for income tax that you should never put on an invoice. They are different numbers for different purposes.
Do I need both an ABN and an ACN if I have a company?
+
Yes. A company must have both. ASIC issues the ACN when you register the company, then the ABR issues the ABN, which is derived from the ACN by adding two check digits to the front. Both numbers must appear on the relevant company documents.
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Sources
- Australian Business Register, apply for an ABN
- ASIC, register a company and get an ACN
- ASIC, fees schedule
General information only, not legal, tax or financial advice. It does not take your circumstances into account. Fees and processes change, so verify current details with the ABR and ASIC or a registered tax agent before acting.
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General information only. This article is educational and does not constitute personal financial advice. It does not account for your circumstances. Consider your own situation and seek advice from a licensed adviser before acting. Read our full disclaimer.
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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