ABN Lookup Australia
Validate any Australian Business Number (ABN) instantly using the official validation algorithm. All checks run client-side — no data is sent to any server.
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About ABNs
An ABN (Australian Business Number) is a unique 11-digit identifier assigned to businesses operating in Australia.
Structure
- Digits 1-2: Check digits (derived from the remaining 9 digits)
- Digits 3-11: Entity identifier (for companies, this is the ACN)
Validation
The first two digits are check digits calculated using a weighted modulus 89 algorithm. This allows instant validation without needing to query a database.
Example ABNs
What is an ABN and Who Needs One?
An Australian Business Number (ABN) is a unique 11-digit identifier issued by the Australian Business Register (ABR) to all entities registered in the Australian Business Register. Introduced on 1 July 2000 as part of the new tax system, the ABN is used for dealings with government agencies, other businesses, and the community.
You need an ABN if you are carrying on an enterprise (business) in Australia. This includes sole traders, partnerships, companies, trusts, government entities, and superannuation funds. An ABN is required to register for GST, claim fuel tax credits, claim GST credits, and avoid having PAYG tax withheld from payments made to you.
Applying for an ABN is free through the Australian Business Register website. The application process is straightforward and most applicants receive their ABN immediately. This tool validates ABN format using the official modulus 89 algorithm — for full business details, use the official ABR lookup service.
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Frequently Asked Questions
What is an Australian Business Number (ABN)?
An Australian Business Number (ABN) is a unique 11-digit identifier issued by the Australian Business Register (ABR) to businesses and other entities operating in Australia. It is used for tax and business identification purposes, and is required for GST registration, invoicing, and interacting with government agencies.
How does the ABN validation algorithm work?
The ABN validation algorithm works by: (1) subtracting 1 from the first digit, (2) multiplying each of the 11 digits by its corresponding weighting factor [10, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19], (3) summing all the products, and (4) dividing the sum by 89. If the remainder is 0, the ABN is valid. This is the official algorithm specified by the Australian Business Register.
Who needs an ABN in Australia?
You need an ABN if you are carrying on an enterprise (business) in Australia, including sole traders, partnerships, companies, trusts, and other entities. You also need an ABN if you want to register for GST, claim fuel tax credits, or avoid having PAYG tax withheld from payments to you. ABNs are free to apply for through the Australian Business Register.
What is the difference between an ABN and an ACN?
An ABN (Australian Business Number) is an 11-digit number for all business entities, while an ACN (Australian Company Number) is a 9-digit number issued only to companies registered under the Corporations Act 2001. A company's ABN is typically formed by adding a two-digit prefix to its ACN. Not all ABN holders have an ACN — only registered companies do.