ABN Validator and ACN Check
Check an ABN or ACN for mistyped digits without querying a register.
Check a business identifier
Validate the ABN Format
An Australian Business Number has 11 digits. This ABN validator removes whitespace, checks the length and applies the ABR’s published ABN calculation.
Subtract 1 from the first digit. Multiply the adjusted digits, in order, by 10, 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19. Add the products. The total must divide by 89 with remainder 0.
The synthetic default ABN 11 123 456 780 produces a weighted total of 445 and passes because 445 divides by 89 exactly. Changing its last digit to 1 produces 464, leaving remainder 19 and failing the check. These numbers identify no client in this example.
Check an ACN
An Australian Company Number has nine digits. Its final digit is calculated from the first eight using ASIC’s ACN check-digit method in Appendix B.
Multiply the first eight digits by 8, 7, 6, 5, 4, 3, 2 and 1. Add the products and take the remainder after division by 10. Subtract that remainder from 10, using 0 when the result is 10. This must equal the ninth digit.
For the synthetic ACN 123 456 780, the weighted total is 120. The remainder is 0, so the expected final digit is 0. Changing the final digit to 1 fails.
ASIC explains that a company’s ABN can contain its ACN with two extra leading digits. ABNs also identify other business types. Passing the ABN test does not establish that its last nine digits are a registered ACN.
Interpret a Passing Check
A passing result means the entered digits satisfy the selected length and arithmetic rules. Different numbers can pass the same rules. The result proves neither current registration nor ownership.
Compare a failing number with the original document before changing it. A calculated check digit is a diagnostic clue, not permission to replace the recorded digit.
When a matter depends on an entity’s identity or current status, obtain current registry information and compare its entity name with the source record. ABN Lookup supplies ABN information. ASIC supplies company information.
Read how to use an ASIC search as registry evidence for the records needed after this local check. Retain those records beside the original identifier.