ABN vs ACN: the difference and which one you need

An ABN is an 11-digit number used to identify an eligible business entity. An ACN is a nine-digit number ASIC issues to an Australian company. A sole trader can have an ABN without an ACN; a trading company will commonly use both.

The distinction matters when you register a name, open an account or issue invoices. Entering a valid number belonging to the wrong entity can leave your records referring to a different business from the one doing the work.

Compare the numbers

Question	ABN	ACN
Full name	Australian Business Number	Australian Company Number
Digits	11	9
Issued through	Australian Business Register	ASIC company registration
Used by	Eligible entities including sole traders, partnerships, companies and trusts	Australian companies
Does it create a company?	No	It identifies the company ASIC has registered
Does it register a trading name?	No	No

ASIC explains the relationship between business and company identifiers. These are identifiers, not endorsements of a business's work or financial position.

Which registrations fit your structure?

A sole trader operates as an individual. Registering a business name doesn't turn that individual into a company. If you've applied for an ABN as a sole trader and a supplier form asks for an ACN, look for an option for a non-company business or ask the supplier how to complete the form.

A partnership has its own registration arrangements. Don't substitute one partner's personal sole trader ABN just because that partner handles the administration.

A company is a separate entity. Start by confirming that you actually want a company, including its ongoing duties and costs. Our business structure comparison covers that decision; the company setup cost guide separates government charges from optional help.

Trust arrangements need particular care. A corporate trustee has an ACN because it is a company, but that doesn't make the trust and trustee interchangeable on forms. Ask your adviser which entity and capacity each application should show rather than copying the first number you find.

If you're registering a company, what comes first?

The ABR's ABN application checklist says a company's ACN is required for its ABN application. You can use the government's Business Registration Service to work through related registrations, but they remain distinct records.

Before submitting anything, create a small registration sheet with the proposed structure, legal entity name, responsible people and the contact email you control. Add the ACN and ABN only when issued. Keep application reference numbers in a different field so they don't get mistaken for completed registrations.

An ABN application through the government registration service is free for eligible applicants. Private providers can charge for assistance. There is a separate government charge for incorporating a company.

Why the numbers can look almost identical

A company's ABN is based on its ACN. ASIC says a company can use its ABN in place of its ACN on company documents where the ABN includes its nine-digit ACN and is used in the same places the ACN would be required. See ASIC's ABN guidance.

Don't generate an ABN yourself by adding two digits to an ACN. Use the issued number and check the corresponding entity record. The relationship isn't a substitute for completing an application or confirming an active registration.

An ABN doesn't mean GST registered

Treat GST status as a separate check. When reviewing a supplier, record the legal entity and ABN, then look at the GST registration information relevant to the transaction. Don't assume a document is a valid tax invoice solely because it contains 11 digits.

Likewise, getting an ABN doesn't register your brand name, reserve a domain or provide an industry licence. Those are separate questions. Our business registration reading guide puts the steps in order so you can work through the ones that apply.

Changing from sole trader to company

The familiar business name can hide an important change: the entity behind it is different. A restructure needs more than replacing a footer on the website.

Use this as a discussion checklist:

• Which entity signs new customer and supplier contracts from the changeover date?
• Which bank and payment accounts receive its income?
• Does the registered business name need to transfer to a new holder?
• Who deals with outstanding invoices and debts from before the change?
• Which tax registrations and software records need separate treatment?

Avoid editing historical invoices indiscriminately. Ask your adviser how to document the transition and retain the earlier entity's records. See our sole trader to company guide for the wider process.

Key takeaways

• An ABN identifies an eligible business entity; an ACN identifies an Australian company.
• Use issued numbers belonging to the entity actually doing the business.
• GST, business names, domains and licences need separate attention.
• When the structure changes, plan the handover of registrations and records.

Where to get help

Check ABN records through ABN Lookup and company records through ASIC's registers. Use our ABN registration guide when you're ready to apply.