These two get confused constantly, mostly because they look similar and often appear in the same conversation about starting a business. They are not the same thing, and knowing the difference matters for registration, invoicing, and compliance.
ABN: your tax and business identifier
An ABN, Australian Business Number, is an 11-digit number issued by the Australian Taxation Office through the Australian Business Register [LegalVision, legalvision.com.au]. Every business in Australia needs one, regardless of structure: sole traders, partnerships, trusts, and companies all apply for an ABN [Lawpath, lawpath.com.au]. It is free to apply for, and you need it to issue tax invoices, register for GST, and generally operate as a business rather than a hobby.
ACN: specific to registered companies
An ACN, Australian Company Number, is a 9-digit number issued by ASIC, used specifically to identify companies registered under the Corporations Act 2001 [LegalVision, legalvision.com.au]. Only companies have an ACN. Sole traders and partnerships cannot get one, because they are not registered as companies in the first place.
Every company automatically receives an ACN when it registers with ASIC, currently at a cost of $611 [ASIC, asic.gov.au]. The ABN, by contrast, is applied for separately and at no cost, even for a company that already has an ACN.
So does a company need both?
Yes. If you register a company, you receive an ACN from ASIC, and you separately need to apply for an ABN through the Australian Business Register to handle your tax obligations [Razorpay, razorpay.com]. The two numbers serve different government bodies and different purposes, but a company genuinely needs both to operate properly.
Quick reference
| ABN | ACN | |
|---|---|---|
| Digits | 11 | 9 |
| Issued by | ATO / Australian Business Register | ASIC |
| Cost | Free | $611 (part of company registration) |
| Who needs it | Sole traders, partnerships, trusts, companies | Companies only |
| Used for | Tax, invoicing, GST registration | Identifying the registered company entity |
If you are setting up a company
Once you have both numbers, you will also need a registered office address for your ACN and a physical address for your ABN. Space Penguin offers virtual addresses in Sydney and Melbourne from $20 per month plus GST, suitable for both. Visit spacepenguin.io/virtual-address to get started.