Key takeaways
- An ABN is an 11-digit number that identifies a business. An ACN is a 9-digit number that identifies a company.
- Sole traders and partnerships use an ABN. Companies receive an ACN from ASIC when they are registered, and most also hold an ABN.
- Changing your business structure may mean applying for a new ABN, so plan the change before you invoice under the new entity.
- Announced Budget changes to trusts and capital gains tax may affect structuring decisions. Check their status before you restructure.
What is the difference between an ABN and an ACN?
ABN vs ACN comes down to what each number identifies. An Australian Business Number (ABN) is an 11-digit number that identifies a business to the government, to other businesses and to the public. An Australian Company Number (ACN) is a 9-digit number that identifies a company. Sole traders and partnerships can hold an ABN, but an ACN belongs to a company.
The two numbers also come from different places. An ABN is registered through the Australian Business Register, which the ATO manages. An ACN is issued by ASIC at the moment a company is registered.
Why does the legal difference between a sole trader and a company matter?
ASIC describes a company as a legal entity that is separate from the people who own and run it. A company must be registered with ASIC under the Corporations Act 2001, and it can get into debt, sue and be sued in its own name. It is owned by its members (shareholders) and has officers who make key decisions.
A sole trader is different. ASIC notes that the business is not a separate legal entity from its owner, and the owner is personally liable for the activities of the business, including all of its debts. That legal difference is why the ACN exists, and it is usually the real question behind an ABN vs ACN search.
Who needs an ABN, an ACN, or both?
Which number you need follows your business structure.
Not everyone needs an ABN. To get one you need to be running a business or other enterprise, and the Australian Business Register publishes entitlement guidance you can check before you apply.
- Sole trader: an ABN. There is no ACN, because a sole trader is not a separate legal entity from its owner.
- Partnership: an ABN.
- Company: an ACN, issued by ASIC on registration. Most companies also hold an ABN.
- Trust: the requirements depend on how the trust is set up and operates. Take advice before applying.
What does an ABN actually let you do?
According to business.gov.au, an ABN lets you verify your business to others when ordering and invoicing, avoid pay as you go (PAYG) tax on payments you receive, claim GST credits and get an Australian (.au) domain name. You also need an ABN before you can register for GST.
Registering for an ABN is free through the Australian Business Register.
How do an ABN and ACN relate on the same company?
ASIC notes that a company's ABN is often its ACN with two extra digits in front. For example, ACN 123 456 789 would correspond to ABN 36 123 456 789. Where this is the case, the company can display its ABN where it would otherwise have to display its ACN.
Companies must show their full name and ACN or ABN on documents including invoices, statements of account, receipts and business letterhead. Check that your invoicing software shows the right number.
Is a business name the same as an ABN or ACN?
No. A business name is a separate registration, handled by ASIC. Your ABN, your ACN if you have one, and your trading name each serve a different purpose. Business.gov.au explains the differences between business names, trading names and legal names, and it is worth confirming which name appears on your ABN record so that your invoices, bank account and registrations all match.
What happens to my ABN if I change structure?
Business.gov.au advises that if you change your business structure you may need to apply for a new ABN, and you have 28 days after becoming aware of a change to update your ABN details.
Illustrative example only: an electrician trading as a sole trader decides to incorporate. The new company is registered with ASIC and receives its own ACN. It is a separate legal entity, so it will need its own ABN, and contracts, bank accounts, supplier accounts, insurance and any GST registration are then reviewed in the company's name. Income and costs need a clean cut-off date so each entity reports only its own transactions.
A structure decision is also a tax decision. The 2026-27 Federal Budget announced changes to the capital gains tax discount, and a minimum 30 per cent tax on discretionary trust distributions proposed from 1 July 2028, with rollover relief for restructuring proposed from 1 July 2027. These are announced measures, and we have not treated them as settled law. Confirm their status before you restructure.
Would a free 30-minute session help?
If you are weighing up a sole trader, company or other structure, a short conversation is often enough to see the practical differences for your circumstances. ANH Accounting is a Sydney advisory firm established in 2018 and a Registered Tax Agent (26258346). You are welcome to book a free 30-minute session to talk it through, with no obligation to proceed.
Frequently asked questions
Can a sole trader have an ACN?
No, because an ACN identifies a company, so a sole trader holds an ABN only unless they set up a company. A company is a separate legal entity, whereas a sole trader and the business are the same.
Is an ABN free?
Yes, business.gov.au states that registering for an ABN through the Australian Business Register is free.
Which number goes on my invoices?
A company must display its full name and its ACN or ABN on invoices, and a sole trader should show their ABN. The ABN can be shown instead of the ACN where the ABN is the ACN with two extra digits in front.
How do I check someone else's ABN?
Use ABN Lookup, the free public register at abr.business.gov.au, to check that a supplier's or client's details are current.
Do I need a new ABN if I change my structure?
You may need one, so check with the Australian Business Register before you start trading under the new entity. Update your ABN details within 28 days of becoming aware of a change.
General information only, last reviewed October 2026. It is not personal advice. Tax law changes, so confirm your circumstances with a registered tax agent or on ato.gov.au.