ABN Validator
Check an ABN or ACN for typing errors before comparing it with the official register.
Check the number’s pattern. Confirm the entity and current registration on the official register.
Enter a number
Choose ABN or ACN, then enter the number to check.
What the Number Check Shows
The ABN validator checks an 11-digit ABN or a nine-digit ACN against its published number rule. It reports the wrong length separately from a failed calculation.
A passing number has the expected pattern. The check does not establish that the number was issued, remains registered or belongs to your client. A client can copy another entity’s number correctly.
Choose the identifier type before entering the number. Spaces are accepted. Other characters make the result unavailable until you remove them. Keep any leading zeros in an ACN.
The entry stays in this page’s memory. It is not sent to a register or saved in browser storage, the page address or an export. Select Clear entry to remove it. Leaving, reloading or returning through browser history also clears it.
How the ABN and ACN Rules Differ
The ABR’s published ABN method subtracts one from the first digit. It multiplies the 11 digits by position weights and adds the products. The total must divide by 89 without a remainder.
ASIC’s ACN method in Appendix D multiplies the first eight digits by weights from eight down to one. The last digit must match the amount needed to reach the next multiple of ten, using zero when the total already divides by ten.
For a fictional arithmetic example, 12 345 678 901 gives an ABN total of 455. Dividing by 89 leaves 10, so the tool reports “Number rule fails”. This is an invented entry, not a client number.
What to Check on the Register
After a pass, use ABN Lookup to compare the entity name and type with your client’s records. Check whether the ABN is active or cancelled and whether its GST registration matches the work you are doing.
For an ACN, compare the company’s name and current registration status through ASIC’s company information. A company and a trust it acts for can be different clients. Confirm which entity is engaging your practice before proceeding.
If a number fails or the register details differ, ask the client to confirm the original record. Changing digits until the calculation passes can leave you with the wrong entity.