Independent service, not affiliated with the ATO, ABR or the Australian Government. Data: ABN Bulk Extract.
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ABN checker

Enter an 11-digit ABN to check if it's a valid number using the official ABR check-digit formula. Spaces are ignored.

Waiting for 11 digits…

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How does the ABN checker work?

ABNs include a built-in check, so typos can be caught without looking anything up. The formula published by the ABR is:

  1. Subtract 1 from the first (left) digit.
  2. Multiply each of the 11 digits by its weight: 10, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19.
  3. Add the results.
  4. Divide the total by 89. If there is no remainder, the ABN is valid.

Example: 51 824 753 556 → (5−1)×10 + 1×1 + 8×3 + 2×5 + 4×7 + 7×9 + 5×11 + 3×13 + 5×15 + 5×17 + 6×19 = 534 = 89 × 6, so it is valid.

A valid check digit only means the number is well-formed — not that it is issued or active. Use the ABN checker and then look the ABN up.