Format of the ABNVersion: 9.9.7
The Australian Business Number (ABN) is a unique 11 digit identifier issued to all entities registered in the Australian Business Register (ABR).
The 11 digit ABN is structured as a 9 digit identifier with two leading check digits. The leading check digits are derived using a modulus 89 (remainder after dividing by 89) calculation.
To verify an ABN:
- Subtract 1 from the first (left-most) digit of the ABN to give a new 11 digit number
- Multiply each of the digits in this new number by a "weighting factor" based on its position as shown in the table below
- Sum the resulting 11 products
- Divide the sum total by 89, noting the remainder
- If the remainder is zero the number is a valid ABN
For example, to check if 51 824 753 556 is a valid ABN:
- Subtract 1 from the first (left-most) digit (5) to give 41 824 753 556
- Multiply each of the digits in 41 824 753 556 by the "weighting factor" based on its position as shown in the table below
- Sum (Digit * weight) to give a total of 534
- Divide 534 by 89 giving 6 with zero remainder.
- As the remainder is zero, 51 824 753 556 is a valid ABN.
Digit | Position | Weighting | Digit * weight |
---|---|---|---|
4 | 1 | 10 | 40 |
1 | 2 | 1 | 1 |
8 | 3 | 3 | 24 |
2 | 4 | 5 | 10 |
4 | 5 | 7 | 28 |
7 | 6 | 9 | 63 |
5 | 7 | 11 | 55 |
3 | 8 | 13 | 39 |
5 | 9 | 15 | 75 |
5 | 10 | 17 | 85 |
6 | 11 | 19 | 114 |
Total: | 534 |
Try your own ABN validation:
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