ABN vs ACN vs ARBN: Australian Business Numbers Explained
Reference for Australian businesses
An ABN identifies your business to the tax system; an ACN identifies a company to the corporate regulator; an ARBN identifies a foreign or registrable body doing business in Australia. Most confusion comes from the fact that a company usually has two of them — and they're nearly the same digits.
ABN — Australian Business Number
An 11-digit identifier issued through the Australian Business Register (administered by the ATO). Every business structure — sole trader, partnership, company, trust — needs one to operate: it's required for invoicing, GST registration, and dealing with other businesses. If you supply goods or services without quoting an ABN, the payer may be required to withhold tax from your payment at the top rate (see the ATO's "no ABN withholding" rules).
ACN — Australian Company Number
A 9-digit identifier issued by ASIC when a company is registered under the Corporations Act. Only companies have one — sole traders and partnerships never do. It must appear on company documents like invoices and contracts. A company's ABN is normally its ACN with two leading check digits added, which is why the two numbers look almost identical.
ARBN — Australian Registered Body Number
A 9-digit identifier issued by ASIC to registrable bodies that aren't Australian companies — most commonly foreign companies registered to carry on business in Australia, and registrable Australian bodies such as some incorporated associations operating interstate.
Which ones do you need?
Sole trader: ABN only. Partnership: ABN for the partnership. Company: ACN on registration, then an ABN for the company. Trust with corporate trustee: the trustee company has an ACN; the trust has its own ABN. Foreign company operating here: ARBN, plus an ABN if it's carrying on an enterprise.
FAQ
Can I have an ABN without an ACN? Yes — every non-company structure does. Can I have an ACN without an ABN? Technically yes (a company that doesn't carry on an enterprise), but almost every trading company needs both. Do the fees differ? An ABN is free to register; company registration and the annual review attract ASIC fees — check the current amounts on asic.gov.au, as they're indexed each July.
Sources: Australian Business Register (ABN); ASIC (ACN, ARBN, fees); ATO (no-ABN withholding). Current as at 24 July 2026. General information, not advice.
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