International · Validation
Australian Company Number (ACN) validator.
Check a 9-digit ACN against the check digit method ASIC publishes, with each step shown. This is the company number issued by ASIC, not the 11-digit ABN issued through the Australian Business Register.
How it works: multiply the first eight digits by 8, 7, 6, 5, 4, 3, 2, 1 and add them. Divide by 10, subtract the remainder from 10 (a result of 10 becomes 0), and the answer must equal the ninth digit.
Inputs
Result
Enter a number and press Check.
How the ACN check digit works
ASIC issues every company a unique 9-digit ACN when it is registered. Its published method calls the last digit a check digit calculated with a modified modulus 10 calculation, and shows ACNs as three blocks of three digits (XXX XXX XXX); the spaces are not part of the number.
| Step | What happens |
|---|---|
| 1 | Weight digits 1 to 8 by 8, 7, 6, 5, 4, 3, 2, 1: 0, 0, 24, 0, 32, 15, 12, 1 |
| 2 | Add them: 84 |
| 3 | Divide by 10: remainder 4 |
| 4 | Complement the remainder to 10: 10 − 4 = 6. If the complement is 10, set it to 0 |
| 5 | 6 equals the ninth digit, so the ACN is valid |
ASIC also notes that a company's ABN is often its ACN with two extra digits in front.
Format check, not an ASIC search
A valid check digit shows the number is well formed, not that a company holds it. Confirm a company on ABN Lookup or through ASIC. For ABNs, use the ABN validator.
Sources
- ASIC: Australian Company Number digit check (archived 2024)
- ASIC: Australian Company Number (9 digits, ABN relationship)
Retrieved October 2026. Rules can change; check the issuing authority if a result matters.
FAQ
How many digits is an ACN?
Nine. ASIC issues a 9-digit Australian Company Number to every company when it is registered.
How is the ACN check digit calculated?
The first eight digits are weighted 8 down to 1 and added. The remainder after dividing by 10 is subtracted from 10, with a result of 10 set to 0. That must equal the ninth digit (ASIC's method).
What is the difference between an ACN and an ABN?
An ACN is the 9-digit company number issued by ASIC. An ABN is an 11-digit number issued through the Australian Business Register. A company's ABN is often its ACN with 2 extra digits at the start.
Does a valid ACN mean the company is registered?
No. The check only shows the digits are well formed. Search ABN Lookup or ASIC to confirm.
Check digit only, not a register lookup
This tool tests the structure and check digit of the number in your browser. It does not query any register, and a passing result does not show the number was issued or is still active. To confirm that, look up the company on ABN Lookup. Nothing you type is transmitted, stored or logged.