Free Tool
ABN Checker
Check an Australian Business Number against the ATO check digit algorithm, format it the way the ABR prints it, and see what an invalid ABN means for your tender response. Runs entirely in your browser.
11 digits. Spaces are ignored.
The ATO builds a check digit into every ABN: subtract 1 from the first digit, multiply the eleven digits by the weights 10, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, and the total must divide evenly by 89. That catches almost every single digit typo and every transposition. It cannot tell you whether the ABN is active, who it belongs to, or whether the entity is registered for GST. Nothing you type here leaves your browser.
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