The short answer
If you are carrying on a business in Australia, put your ABN on every invoice. It is required on a tax invoice, and even on a plain invoice its absence triggers a withholding obligation for your customer that costs you nearly half the payment until you sort it out.
What happens when the ABN is missing
Where a business makes a payment to a supplier who has not quoted an ABN, the payer is required to withhold 47% of the invoice amount and remit it to the ATO. That has been the rate since 1 July 2017. Your customer is not being difficult — they are following the no-ABN withholding rules, and they carry the liability if they get it wrong.
"Not quoting an ABN" means the number was not on the invoice and you did not supply it any other way. If your ABN is on a purchase order, a contract, or another document relating to the supply, that counts. The withholding does not apply if:
- The invoice or another document relating to the supply quotes your ABN
- Your agent's ABN is quoted, where the supply is made through an agent
- You are not entitled to an ABN, or one of the ATO's exceptions applies
Those exceptions are narrow: supplies that are private or domestic for the supplier, hobby or private recreational activity, and a handful of others. If you are invoicing for work, assume the rule applies to you.
ABN and GST registration are not the same thing
| ABN | GST registration | |
|---|---|---|
| Who needs it | Anyone carrying on an enterprise | Turnover of $75,000 or more, or by choice below that |
| Goes on the invoice | Always | Determines whether you charge GST at all |
| Document you issue | Invoice | Tax invoice, with the GST shown |
| If you get it wrong | Customer withholds 47% | You may owe the ATO GST you charged but were not entitled to |
So there are three normal states: no ABN and not in business; ABN without GST registration, which invoices with no GST line; and ABN with GST registration, which issues tax invoices showing GST.
Checking someone else's ABN
Before paying a new subcontractor, it is worth confirming their ABN is active and matches the name on the invoice — a lapsed ABN puts the withholding obligation back on you. The ABN Lookup service at abr.business.gov.au is free and shows registration status and GST registration dates.
Where to put it
There is no required position — near your business name at the top is the convention, and it is where a bookkeeper will look. What matters is that it is legible on the document itself, not just in your email signature.
The reliable fix is to make it impossible to forget: store the ABN in your invoicing settings once so every document carries it. That is how JASC handles it — business details live in settings and print on every quote and invoice, alongside the GST breakdown.
Source
Withholding rules on this page come from the ATO's guidance on withholding if an ABN is not provided and the statement by a supplier not quoting an ABN. General information only, not tax advice.