Free tool
ABN checker
Paste an ABN. It tells you straight away whether the number is real.
Every Australian Business Number carries a check digit. Paste one in above and this page works out, without asking anything of anyone, whether the number is well formed or whether a digit is wrong.
That is a real test and it is worth running. A mistyped ABN on an invoice fails it. So does an invented one.
What a valid checksum does and does not tell you
It tells you the eleven digits are internally consistent, so the number was not invented or fat fingered.
It does not tell you the ABN is active, who holds it, whether the holder is the business you are dealing with, or whether they are registered for GST. Those four things come from the Australian Business Register, and the link to that exact ABN appears once the number checks out.
How the check works
Subtract one from the first digit. Multiply each of the eleven digits by its weight, which runs 10, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19. Add the results. If the total divides by 89, the number is valid. The Australian Taxation Office publishes the algorithm, which is why this page can run it rather than ask a server.
What to check once you get to the register
- Active. A cancelled ABN on a current invoice is a problem, not a formality.
- GST registered. If an invoice charges GST, the ABN on it should be registered for GST. If it is not, the GST line should not be there.
- The entity name. It will often differ from the trading name, which is normal. What is not normal is an entity with no visible connection to the business you are dealing with.
- The registration date. A business trading for fifteen years under an ABN registered last month is worth a question.
Why it matters on an invoice
If a supplier does not quote an ABN on an invoice, the payer may be required to withhold tax from the payment at the top rate. That is the ATO rule and it is the practical reason ABNs appear on invoices at all.
An ABN is not a licence. Almost anyone can get an ABN in about ten minutes. A licence is permission to do a specific class of regulated work. Check both, separately, and the licence check is the other half of the job.
Common questions
Does this tell me if the ABN is active?
No. It validates the checksum, which proves the number is well formed rather than mistyped or invented. Active status, the entity name and GST registration all come from the Australian Business Register, and the link to that exact ABN appears once the number checks out.
Is my ABN sent anywhere?
No. The check runs in your browser using the algorithm the ATO publishes. Nothing leaves the page, there is no request, and there is nothing to log.
Is an ABN the same as a licence?
No, and the difference matters. An ABN is a tax registration and almost anyone can get one. A licence is permission to do a specific class of regulated work. Check both, separately.
What is the difference between an ABN and an ACN?
An ACN is a nine digit company number issued by ASIC and only companies have one. An ABN is eleven digits, issued by the ATO, and sole traders, partnerships, trusts and companies can all have one. A company ABN usually contains its ACN.
The checksum passes but the entity name is different. What now?
Ask. Trading names routinely differ from the registered entity and that is normal. An entity with no visible connection to the business in front of you is not.