An ABN is an eleven-digit Australian Business Number, issued by the Australian Business Register to any entity carrying on an enterprise. An ACN is a nine-digit Australian Company Number, issued by ASIC when a company is registered. Sole traders, partnerships and trusts have an ABN and no ACN. A company has both — it gets its ACN at registration and then applies for an ABN, and its ABN is its ACN with two extra digits at the front.
Side by side
| ABN | ACN | |
|---|---|---|
| Stands for | Australian Business Number | Australian Company Number |
| Issued by | The Australian Business Register, administered by the ATO | ASIC |
| Format | Eleven digits | Nine digits |
| Who has one | Any entity carrying on an enterprise — sole traders, partnerships, companies, trusts | Companies only |
| What it identifies | A business, for dealings with the ATO and with other businesses | A company, as a legal entity registered under the Corporations Act |
| Cost | Free | Issued as part of company registration, which carries an ASIC fee indexed each year |
| Ongoing obligations | Keep the details current and notify changes within 28 days | Annual statement and annual review fee, for as long as the company exists |
| Public register | ABN Lookup at abr.gov.au | ASIC company register |
Which one do I need?
This is not really a choice between two numbers. It is a consequence of the business structure you picked, and it follows automatically:
- Sole trader — ABN only. One ABN in your own name, covering every business you run as a sole trader.
- Partnership — ABN only, issued to the partnership as an entity separate from the partners' own ABNs.
- Trust — ABN only for the trust. If the trustee is a company, that company has its own ACN and usually its own ABN as well.
- Company — both. ASIC issues the ACN when the company comes into existence; the ABN comes afterwards and is optional in law but unavoidable in practice, because without one every business customer must withhold tax from your payments.
If nobody has registered a company for you, you do not have an ACN and you do not need one. Wanting to look bigger is not a reason to incorporate — the running costs and the director obligations are real, and they arrive whether or not the company trades.
Why a company's ABN contains its ACN
When a company applies for an ABN, the Registrar builds the number by taking the nine-digit ACN and prefixing two check digits. So a company with ACN 123 456 789 ends up with an ABN of the form xx 123 456 789. This is genuinely useful:
- You can read a company's ACN straight off its ABN — the last nine digits.
- ASIC accepts the ABN in place of the ACN on public documents, provided the last nine digits of the ABN are identical to the ACN. That is why most Australian company invoices show an ABN and no separate ACN line.
- If a company shows you an ABN whose last nine digits are not its ACN, something is wrong — check both on the public registers before you extend credit.
Where each number has to appear
Both are public identifiers and both are meant to be visible.
- Your ABN belongs on every invoice you issue. It is one of the seven things a valid tax invoice must show, and leaving it off triggers no-ABN withholding at the top rate — see how to invoice with GST.
- A company must show its ACN (or a qualifying ABN) on its public documents — invoices, receipts, orders, cheques, notices and its website. The company name must appear as well.
- Both registers are free and public. ABN Lookup at abr.gov.au tells you whether an ABN is active and whether that entity is registered for GST. ASIC's company register tells you whether a company exists, who its directors are, and whether it is in liquidation.
Checking a new client on both before you start work costs two minutes. A supplier charging you GST while not registered for it is a GST credit you cannot claim on your BAS.
How to get an ACN
You do not apply for an ACN on its own. It is issued as a by-product of registering a company, either directly with ASIC through ASIC Connect or through a private service provider, an accountant or a lawyer. The sequence is:
- Decide the company details — name, whether it is proprietary limited, share structure, registered office, and who the directors and shareholders are.
- Get a director ID for every director. This is a separate identifier from the Australian Business Registry Services, it must be obtained by the individual personally, and it is required before appointment. It is free.
- Register the company with ASIC. The fee is set by ASIC and indexed annually, so check the current amount at asic.gov.au rather than trusting a figure in an article.
- The ACN is issued on registration, along with the certificate of registration.
- Apply for the company's ABN through the Australian Business Register, which is free, and register for GST at the same time if the company will need it.
Registering a company also commits you to an annual review fee and an annual statement every year, whether or not the company earned anything. That recurring cost is the main reason not to incorporate before you need to.
The numbers that are not an ABN or an ACN
| Number | What it is |
|---|---|
| TFN | Your Tax File Number. Private, personal, and never printed on an invoice. A company has its own TFN, separate from yours. |
| ARBN | Australian Registered Body Number — for foreign companies and other bodies registered with ASIC that are not Australian companies. |
| Director ID | A permanent identifier every company director must obtain personally from Australian Business Registry Services before being appointed. Free, and it stays with you for life. |
| Business name | Not a number at all. A name registered with ASIC so you can trade under something other than your own name. It creates no legal entity. |
| GST registration | A status attached to your ABN once turnover crosses the threshold, not a separate number. Having an ABN does not mean you charge GST. |
Related reading
- How to get an ABN — the free application, step by step
- Sole trader, partnership, company or trust? — decide this before you register anything
- How to register a business name — a third, separate registration
- How to start a business in Australia — where each registration fits in the order
Frequently asked questions
No. An ACN only exists for companies. As a sole trader you have an ABN in your own name and that is the only business identifier you need. If you later register a company, that company is a separate legal entity and gets its own ACN and its own ABN.
Technically yes — the ACN is issued by ASIC on registration and applying for an ABN is a separate step. In practice a company without an ABN cannot operate normally, because every business customer paying it would have to withhold tax at the top rate, and it cannot register for GST.
Search the company name on ASIC’s register, or read it off its ABN — for a company the last nine digits of the ABN are the ACN. ABN Lookup at abr.gov.au will also show the ACN against a company ABN, along with whether the entity is registered for GST.
No. An ACN is a number that identifies a company as a legal entity. A business name is a name registered with ASIC so you can trade under something other than your own or your company’s legal name. They are separate registrations with separate fees, and a company can have several business names.
There is no fee for the number itself — it is issued as part of registering a company, and ASIC charges a registration fee for that. ASIC indexes its fees annually, and there is also an annual review fee every year the company stays registered, so check the current amounts at asic.gov.au.
Sources
ABN entitlement and the structure of a company's ABN come from the Australian Business Register; company registration, ACN display obligations, director IDs and fees come from ASIC. Fees are indexed annually — confirm the current position at asic.gov.au, abr.gov.au or with a registered tax agent. Balaana is bookkeeping software, not a tax agent — this article is general information, not personal tax advice.