An ACN identifies a company, while an ABN identifies a business for tax purposes — and whether you need one or both depends entirely on your business structure.
If you’re starting or running a business in Australia, understanding the difference between an ACN and an ABN is essential. These numbers affect how you register your business, issue invoices, meet tax obligations, and operate legally. While they’re often mentioned together, they serve very different purposes.
This guide explains ACN vs ABN clearly, so you know exactly what applies to your situation.
What Is the Difference Between an ACN and an ABN?
The key difference comes down to legal structure vs tax identification.
- An ACN (Australian Company Number) identifies a registered company
- An ABN (Australian Business Number) identifies a business entity for tax and commercial purposes
Not every business needs both.
What Is an ACN (Australian Company Number)?
An ACN is a 9-digit number issued by ASIC to companies only.
It confirms that a business is legally registered as a company under Australian law and exists as a separate legal entity.
You need an ACN if you:
- Operate as a Pty Ltd or public company
- Want legal recognition as a separate entity
- Are required to comply with corporate regulations
An ACN must appear on official company documents such as:
- Invoices
- Contracts
- Company websites
- Letterheads
Sole traders, partnerships, and trusts do not receive an ACN.
What Is an ABN (Australian Business Number)?
An ABN is an 11-digit number issued through the Australian Business Register and managed by the ATO.
It identifies a business for:
- Tax reporting
- GST registration
- Invoicing
- Business verification
You may need an ABN if you:
- Run a business or side hustle
- Invoice clients
- Want to avoid PAYG withholding
- Register for GST
- Operate commercially in Australia
Unlike an ACN, an ABN can apply to sole traders, partnerships, trusts, and companies.
ACN vs ABN: Key Differences at a Glance
| Feature | ACN | ABN |
|---|---|---|
| Issued by | ASIC | Australian Business Register |
| Number of digits | 9 | 11 |
| Who needs it | Companies only | Most business types |
| Purpose | Legal company identification | Tax and business identification |
| Mandatory? | Yes, for companies | Depends on business activity |
Do You Need Both an ACN and ABN?
This depends on your business structure:
- Companies → Usually need both an ACN and an ABN
- Sole traders → Usually need only an ABN
- Partnerships & trusts → Typically need an ABN only
If you operate as a company, your ABN is linked to your ACN.
Is the ACN the Last 9 Digits of the ABN?
Yes — in most cases for companies.
When a company applies for an ABN, the ATO typically uses the nine digits of the ACN and adds a two-digit prefix to create the 11-digit ABN. This links the company across government systems and simplifies identification.
Benefits of Having an ACN
If you operate as a company, an ACN provides important advantages:
- Confirms your legal status as a registered company
- Builds credibility with clients and suppliers
- Enables limited liability protection
- Allows company-level tax arrangements
- Makes it easier to raise capital or add shareholders
An ACN also separates your personal identity from your business obligations.
Benefits of Having an ABN
An ABN helps your business operate professionally and compliantly:
- Allows you to legally operate as a business in Australia
- Prevents PAYG tax being withheld from your income
- Enables GST registration when required
- Helps clients and suppliers verify your business
- Allows you to claim business-related expenses
- Provides access to wholesale pricing and business services
An ABN is essential for running a business smoothly.
Do I Need an ABN to Get an ACN?
No — it works the other way around.
You must register your company first to receive an ACN.
Once you have your ACN, you can then apply for an ABN through the Australian Business Register if your company is trading or conducting business activities.
Do I Need an ABN If I Earn Under $75,000?
Yes, you may still need an ABN.
- GST registration is only mandatory once turnover exceeds $75,000
- However, an ABN may still be required to:
- Invoice clients
- Avoid PAYG withholding
- Operate legitimately as a business
GST may be optional below $75,000, but an ABN often isn’t.
FAQs About ACN and ABN
Can you run a business without an ABN?
Yes, but it’s usually impractical. Clients may withhold tax, and the business may appear less professional.
Is an ABN the same as a business name?
No. A business name is what customers see; an ABN is how the government identifies your business.
Do I need an ACN as a sole trader?
No. Sole traders never receive an ACN — only companies do.
Can I have more than one ABN?
No. Each business entity can only have one ABN.
Can I have an ACN without an ABN?
Yes, if the company is not trading. Once it starts business activities, an ABN is required.
Does an ABN cost money?
No. Registering for an ABN is free. Company registration to obtain an ACN includes ASIC fees.
How long does it take to get an ABN?
Most ABN applications are processed instantly online if all details are provided correctly.
Can an ABN be cancelled?
Yes. If you stop operating, your ABN should be cancelled to avoid compliance issues.
Get Expert Help With Your Business Setup
Choosing the right business structure from the start can save you time, money, and compliance headaches.
At Infinity22, our certified practising accountants provide end-to-end support — from company registration and ABN applications to bookkeeping, tax compliance, and ongoing business advice.
Ready to get your business foundations right?
Book a free consultation today and let our experts guide you through every step.
