Australia ABN Generator
Online generator for Australian Business Number (ABN) issued by the ATO for software testing and invoicing QA.
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About the Australian Business Number (ABN)
The Australian Business Number (ABN) is a unique 11-digit identifier issued by the Australian Taxation Office (ATO) and registered in the Australian Business Register (ABR).
It identifies businesses, sole traders, partnerships, and government entities for tax invoices, Goods and Services Tax (GST) reporting, and commercial transactions across Australia.
Anatomy & Structure of the ABN (Australian Business Number)
The Australian Business Number consists of 11 digits structured in 2 parts:
| Position | Field | Length | Meaning & Rule | Example |
|---|---|---|---|---|
| 1 & 2 | Weighted Check Digits | 2 digits | Integrity check digits calculated via Modulo 89 (with 1 subtracted from 1st digit) | 51 |
| 3 to 11 | ACN / Base Identifier | 9 digits | Matches the 9-digit Australian Company Number (ACN) or unique ATO sequence | 824753556 |
Official Algorithm (Weighted Modulo 89 — ATO)
Official check algorithm for Australian Business Number:
S = ((d[0] - 1) * 10) + Σ (d[i] * W[i]) (i=1..10); Valid if S mod 89 === 0
- 1. Subtract 1 from the first digit (position 1).
- 2. Multiply the 11 digits by weights: W = [10, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19].
- 3. Sum all weighted products to get total S.
- 4. Compute remainder of S divided by 89.
- 5. The ABN is valid if and only if remainder is exactly zero (S mod 89 = 0).