ABN vs ACN: What’s the Difference and Which Do You Need?

By Bilal Alwan, Manager, Hunters Hill Offices · Updated October 2026

ABN vs ACN trips up a lot of new business owners. Both are government numbers, both appear on invoices, and a company’s two numbers can look almost identical. They come from different agencies, though, and they do different jobs.

This guide explains what each number is, who needs which, and what each register shows about your business address. Every fact below was checked against ASIC and Australian Business Register pages in October 2026.

ABN vs ACN: The Quick Difference

	ABN	ACN
Length	11 digits	9 digits
Issued by	Australian Business Register (ATO)	ASIC
Who gets one	Entities carrying on an enterprise, plus companies registered with ASIC	Companies, when they register with ASIC
Sole traders	Yes, if running a business	No
Companies	Entitled to one, and most have one	Always
Public address shown	State and postcode only	The companies register shows the principal place of business

What Is an ABN?

Business.gov.au describes an ABN as a unique 11-digit number that identifies your business to the government, other businesses and the public. Applying through the Australian Business Register is free.

Not everyone is entitled to one. The ABR says you must be running a business. If you have been engaged to work as an employee, you are not entitled to an ABN for that work.

A few other ABR rules worth knowing:

• As of October 2026, you must update your ABN details within 28 days of becoming aware of a change, such as a new address.
• Most people with an ABN must lodge an annual income tax return, whether the business makes a profit or a loss.
• You are only entitled to keep an ABN while you are running an enterprise.
• You may still need an ABN even if your turnover is below the GST threshold.

You can check an ABN, or apply for one, on the Australian Business Register.

What Is an ACN?

ASIC says an ACN is a unique 9-digit number that identifies a company. ASIC issues every company with an ACN when it is registered. You do not apply for an ACN on its own: it arrives with your registration, along with your certificate.

Some bodies registered with ASIC that are not companies, such as foreign companies, get a different 9-digit number called an ARBN. Most small businesses will never need one.

Where your ACN must appear

According to ASIC’s ACN page, a company must show its ACN on documents such as:

• invoices and statements of account
• orders for goods and services
• business letterhead
• documents it lodges with ASIC

ASIC also lists items that do not need the ACN, including business cards, envelopes, vehicles and advertisements.

Do You Need an ABN, an ACN or Both?

It comes down to your business structure. If you are weighing that up, start with our guide to sole trader vs company.

Sole traders

You need an ABN if you are running a business. You will not have an ACN, because you are not a company. If you trade under a name other than your own first name and surname, you will also need to register a business name with ASIC, and ASIC requires an ABN to do that.

Companies

Your company gets an ACN from ASIC on registration. Companies registered with ASIC are also entitled to an ABN, and ASIC says most companies have both.

Here is the handy part. A company’s ABN is often its ACN with two extra digits at the front. ASIC’s example is ACN 123 456 789 and ABN 36 123 456 789. When that is the case, the company can show its ABN where it would usually have to show its ACN.

ABN vs ACN: What Each Register Shows About Your Address

If you run a business from home, this is the part that matters most. The two registers treat your address very differently.

ABN Lookup only shows the state and postcode of your main business location. The ABR says it does not include your street address, email or phone number.

The ASIC companies register is more open. Anyone who searches it can see your company’s principal place of business, which is where the company actually conducts business. People who purchase information from the register can also see the registered office. Directors’ home addresses appear too, unless ASIC agrees to hide one for safety reasons.

Your registered office can be a third-party address, such as a virtual business address, as long as you keep the occupier’s written consent. Your principal place of business must be where the business is really run. If that is your home, a virtual address will not change what the register shows. We explain both in principal place of business vs registered office.

Getting Your Numbers Right: A Quick Checklist

1. Choose your structure first, because it decides which numbers you need.
2. Sole trader: apply for an ABN through the ABR.
3. Company: register with ASIC to get your ACN, and make sure the company has its own ABN.
4. Put the right number on invoices, orders and letterhead.
5. Update your ABN details within 28 days of a change, and tell ASIC within 28 days if a company address changes (both as of October 2026; see the ABR and ASIC).

This is general information, not tax or legal advice. Check your situation with your accountant, the ABR or ASIC.

Once the ABN vs ACN question is settled, the next decision is which address goes on those registrations. A Hunters Hill virtual office gives you a street address that can be used as your ASIC registered office, with mail and parcels handled for you. New to the idea? Start with what a virtual office is.