Tax & ATO
Australian Business Number
An Australian Business Number (ABN) is a unique 11-digit identifier issued free by the Australian Business Register to entities carrying on an enterprise in Australia. It must appear on your tax invoices and links your GST, PAYG and other registrations. If a supplier provides no ABN, the payer must generally withhold 47% of the payment.
The ABN is the public-facing identifier of an Australian business. You apply through the Australian Business Register at abr.gov.au, the application is free, and in straightforward cases the number issues immediately. To be entitled to an ABN you must be carrying on (or starting) an enterprise: an employee cannot get one for their job, and a hobby is not an enterprise. Each business structure holds its own ABN. A sole trader's ABN attaches to them personally and follows them across ventures; a company, partnership or trust applies with the entity's own TFN and receives an entity ABN. A company's ABN is its nine-digit ACN with two check digits added in front.
The ABN does not replace the TFN: the TFN is your private tax identifier, while the ABN is quoted publicly on invoices, contracts and registrations. GST, PAYG withholding, and fuel tax credit registrations all hang off the ABN, and anyone can confirm your registration status, GST registration and business name in seconds through ABN Lookup. Details such as address and main activity must be kept current, generally within 28 days of a change, and the Registrar can cancel ABNs that show no business activity.
Practically, you cannot invoice properly without one. A tax invoice must show the seller's identity and ABN, so a missing ABN makes every invoice you issue defective and blocks your GST-registered customers from claiming credits. More painfully, the no-ABN withholding rule applies: when a business pays a supplier who has not quoted an ABN, it must generally withhold 47% of the payment and send it to the ATO. On a $10,000 invoice, that means receiving $5,300 and waiting until your tax return to recover the withheld $4,700. The ATO explains the rule in its guidance on withholding from suppliers on ato.gov.au.
The ABN is also how counterparties vet you. Landlords, insurers, wholesale suppliers and government tender panels routinely check ABN Lookup before dealing with a business, and an ABN that is cancelled or shows no GST registration when you have been charging GST is a red flag. Check any supplier or customer with the OneBookPlus ABN lookup tool before you rely on their details.
Apply directly at the Australian Business Register: it is free, and the same application can register you for GST, PAYG withholding and a business name at the same time. Be wary of unofficial websites that charge $50 to $100 to lodge the same free form; the ABR itself never charges for an ABN.
Keeping the ABN healthy is mostly housekeeping. Update your details within 28 days when your address, main activity, or authorised contacts change. If you stop trading, cancel the ABN rather than letting it sit, because a dormant ABN kept alive still attracts lodgement expectations for linked registrations. If your ABN is cancelled for inactivity but you are genuinely still in business, you can reapply and will usually get the same number back.
Do not confuse the ABN with the ACN. The ACN is the nine-digit company identifier ASIC issues when a company is registered; only companies have one. The ABN identifies any business structure for tax and invoicing, which is why a sole trader has an ABN but no ACN, while a company has both.
The definitions above only get you so far; the free OneBookPlus ABN lookup tool turns them into your own figures in seconds, no sign-up needed.
No. Applying through the Australian Business Register at abr.gov.au is free. Third-party websites that charge a fee are lodging the same free application on your behalf. Registering a business name with ASIC does carry a fee, but the ABN itself never does.
The $75,000 figure is the GST registration threshold, not an ABN threshold. If you are carrying on an enterprise of any size you should hold an ABN, otherwise your business customers must withhold 47% from payments to you. GST registration remains optional until turnover reaches $75,000.
An ABN is an 11-digit identifier any business structure uses for tax and invoicing. An ACN is a nine-digit number ASIC issues only to registered companies. A company holds both, and its ABN is its ACN with two extra digits in front; sole traders and partnerships have only an ABN.
Last reviewed and updated: by Bishal Shrestha