Verifying Australian ABNs for Shopify Wholesale (and What GST Registration Actually Tells You)
An Australian retailer applies for a wholesale account and types an 11-digit ABN into your form. It has the right number of digits. Is it theirs? Is it active? Are they actually registered for GST, which changes how your invoices to them should look?
You can answer all three in under a second, for free, against the official register — which makes Australia the strange case in international B2B verification: the easiest registry to integrate, and still one of the least-checked numbers on wholesale forms.
TL;DR: ABNs verify against the Australian Business Register's free ABN Lookup API, which returns the entity's registered name, ABN status, and GST registration. Validate the checksum locally (ABNs have a built-in check digit algorithm — most typos never need an API call), then confirm live and cross-check the returned entity name against the application. GST registration matters for invoicing, not for exemption: Australian domestic B2B sales carry GST, which registered buyers claim back as input tax credits — so ABN verification is about legitimacy and correct treatment, not about zero-rating anyone.
What an ABN Is (and Isn't)
The Australian Business Number is an 11-digit identifier for entities carrying on business in Australia — companies, sole traders, partnerships, trusts. It's public, searchable, and designed for exactly the use case of one business checking another. Two related numbers cause confusion: the ACN (a 9-digit company number issued by ASIC, embedded inside company ABNs) and the GST registration, which is a status attached to an ABN, not a separate number. A business can hold a valid ABN and not be registered for GST — perfectly legal below the turnover threshold, and exactly the kind of detail a form field can't tell you.
The Three-Step Check
1. Checksum locally. ABNs carry a weighted check-digit algorithm, so an ABN with a transposed digit fails arithmetic before any API is involved. Instant feedback on the form, zero API calls wasted on typos.
2. Look it up on the ABR. The ABN Lookup API is free (register for an authentication GUID) and returns the entity's registered name, entity type, ABN status — active or cancelled, with effective dates — and GST registration status.
3. Cross-check the name. The registered entity name comes back with the lookup; compare it to what the applicant typed. As with VIES in the EU and HMRC in the UK, a valid number that belongs to a different entity is the failure mode that format checks and even live lookups miss if nobody compares names. Trading-name-vs-legal-name mismatches are common and innocent; they're still worth a human glance rather than an auto-pass.
| Check | Catches | Cost |
|---|---|---|
| Checksum (local) | Typos, fabricated numbers | Free, instant |
| ABR status lookup | Cancelled ABNs, deregistered entities | Free API |
| GST registration flag | Wrong invoice treatment assumptions | Included in lookup |
| Entity-name cross-check | Borrowed/mismatched ABNs | Included — if you compare |
The Part That Isn't Like Europe: GST Doesn't Get Exempted
If your mental model comes from EU VAT, unlearn one thing for Australia: there is no reverse-charge-style exemption for ordinary domestic B2B sales. An Australian merchant selling to an Australian GST-registered business charges GST as normal; the buyer claims it back as an input tax credit on their BAS. Nobody gets zero-rated for being a business.
So what does the GST flag buy you? Correct paperwork and correct expectations. A GST-registered buyer needs a tax invoice with your ABN and the GST shown to claim their credit — and a buyer claiming GST registration the ABR says they don't have is either confused or misrepresenting, both worth knowing at approval time. (Exports are their own topic — GST-free treatment for goods leaving Australia has its own conditions — and that, like all of this, is your accountant's domain, not a form field's.)
This is why ABN verification belongs in the approval decision rather than the tax configuration: it establishes that the business is real, currently registered, and accurately describing itself. For Australian merchants, that's the entire wholesale-gate question; for international merchants selling into Australia, it's the legitimacy check before anything else.
Frequently Asked Questions
How do I verify an ABN is real? Checksum first (the 11 digits carry a built-in check algorithm), then the ABR's free ABN Lookup API for live status, registered name, and GST registration. Both halves matter: the checksum catches typos, the lookup catches cancelled and borrowed numbers.
Does a valid ABN mean the buyer is GST-registered? No. GST registration is a separate status the lookup reports. Businesses under the turnover threshold can legitimately hold an ABN without GST registration — which changes what your invoice to them means.
Should Australian B2B customers be tax exempt on Shopify? For domestic sales, no — GST applies to B2B and registered buyers reclaim it as input credits. ABN verification supports the approval decision and correct invoicing, not a tax exemption.
What's the difference between an ABN and an ACN? The ACN is a 9-digit company number from ASIC; companies embed it in their 11-digit ABN. Wholesale forms should ask for the ABN — it covers all entity types and is what the ABR lookup keys on.
B2B Onboard validates ABNs during registration — checksum on the form, live ABR lookup for status and GST registration, entity name cross-checked against the application. Verified Australian businesses can auto-approve; mismatches and cancelled ABNs queue for your review. See how it works.
Peer Jakobsen is the founder of Mentilead. He builds Shopify B2B apps from Denmark with a focus on clean architecture and EU compliance.