What must legally be on an Australian tax invoice

An invoice is a legal document doing a specific job: it’s the evidence your customer needs to claim a GST credit. If it’s missing a required field, they can’t claim, and a $4,400 invoice has just cost them $400 they expected to get back. They will notice, and you’ll be reissuing it.

The requirements are short and stable. Most invoicing problems come from not knowing there was a list at all.

General information, not tax advice. The ATO is the authority - see ato.gov.au or ask a registered tax or BAS agent.

For sales under $1,000

A tax invoice must include all of these:

1. The words “Tax invoice”. The ATO requires enough information to clearly determine that the document is intended to be a tax invoice; putting those words prominently at the top is the plainest way to do that, and a document headed only “Invoice” leaves it open to argument.
2. Your identity - your business or trading name.
3. Your ABN.
4. The date the invoice was issued.
5. A description of what was sold - enough to identify the items, and the quantity where it’s relevant.
6. The GST amount, either shown as a separate line, or covered by a statement such as “Total price includes GST” where GST is exactly one-eleventh of the total.

That last option only works when every line is taxable at 10%. If your invoice mixes taxable and GST-free items - some food, some medical services, some education - the shortcut breaks, and you must show clearly which items are taxable and what the GST is.

For sales of $1,000 or more

Everything above, plus one more:

7. The buyer’s identity or ABN - their business name or their ABN.

This is an easy one to miss, because most people build one template and never revisit it. The template works fine for eighteen months of small jobs, then a $6,000 invoice goes out in the same format and it’s not compliant. If most of your work is over the threshold, just include the customer’s details on everything and stop thinking about it.

If you’re not registered for GST

You don’t issue tax invoices at all - you issue a plain invoice, and it must not say “tax invoice” or show any GST amount. Charging GST when you aren’t registered is a real problem, not a formatting one.

Your invoice should still show your name, your ABN, the date, a description of the work, and the total. You may want to note that no GST has been charged, which pre-empts the question from customers who assume every invoice has GST in it. If you’re not sure whether you’ve crossed the threshold yet, see GST registration and BAS for sole traders.

Why the ABN matters more than people think

If you don’t quote an ABN on an invoice, a business customer is generally required to withhold the top rate of tax, currently 47% from the payment and send it to the ATO. Not as a penalty - as a legally required withholding.

In practice, what happens is that your invoice lands in someone’s accounts payable queue, the ABN field is empty, and the whole thing stops. You find out weeks later when you chase the payment. It’s an entirely avoidable delay caused by one missing line.

Getting paid: the parts that aren’t legally required

Compliance gets your invoice accepted. It doesn’t get it paid. These do (see how to get invoices paid on time for the follow-up side of this):

An invoice number. Sequential, unique, and never reused. It’s how you and your customer refer to the invoice in every subsequent conversation, and it’s how you’ll find it in two years when someone queries it. “The one from March” is not a reference.

Explicit payment terms. Not “payable on receipt” - a date. “Due 14 days from issue: 25 February 2026.” Ambiguity always resolves in favour of paying later. A specific date converts a vague intention into something with a deadline, and it’s what makes a follow-up on the 26th reasonable rather than pushy.

Complete payment details. BSB, account number, and account name, exactly as the bank has it. A mismatched account name will bounce the transfer. If you accept card payments, say so and say whether there’s a surcharge.

A payment reference you’ve told them to use. Usually the invoice number. Without one you get deposits landing in your account labelled “TRANSFER” and no idea which invoice they clear.

Their reference, if they gave you one. Purchase order numbers exist because larger organisations genuinely cannot pay an invoice without one. If your customer issued a PO, put it on the invoice.

A description a stranger can understand. The person paying is often not the person who hired you. “Consulting - June” tells them nothing and invites a query. “Website redesign - stage 2 of 3, as per quote Q-104” can be approved without a phone call.

Contact details. So a question about the invoice becomes an email to you rather than a reason to put it aside.

Adjustment notes

When something is wrong with an invoice you’ve already issued, you don’t edit it and re-send. Where the document simply got a detail wrong, a corrected tax invoice that makes clear it replaces the original is the usual fix. Where the sale itself changed after the fact - the price altered, part of it was cancelled, a credit was given - an adjustment note (what most people still call a credit note), referencing the original invoice, is what the GST rules call for. Which one applies is worth checking with a registered tax or BAS agent on anything substantial.

The reason is straightforward: your customer may have already claimed a GST credit based on the original document. Both sides need a paper trail showing what changed and when. Quietly editing a sent invoice leaves two different versions of the same numbered document in the world, which is a problem for both of you at audit time.

The same logic applies to any change after issue. Once an invoice has gone out, it’s a fixed record. Corrections happen through new documents, not edits.

Record keeping

Under the ATO’s record keeping rules for business, you must keep your records - invoices, receipts, and the documents supporting them - for five years from when the transaction was completed or the record was prepared, whichever is later. Digital copies are fine, provided they’re a true and clear reproduction and you can actually produce them on request.

That last clause deserves attention. “I have them somewhere” is not the same as being able to produce them. Five years is long enough that laptops die, phones get replaced, and the cloud service you were using shuts down or changes its export format. Whatever system you use, the test is whether you could retrieve an invoice from four years ago this afternoon.

The compliance checklist

Before you send:

• The words “Tax invoice” appear (if you’re GST-registered)
• Your business name and ABN
• Date of issue
• A unique invoice number
• Clear description of goods or services, with quantities where relevant
• GST shown separately, or the “includes GST” statement where it applies
• The customer’s name or ABN, if the sale is $1,000 or more
• Total payable
• A specific due date
• Bank details and the reference to use

Ten items, and eight of them never change between invoices. This is exactly the kind of thing worth setting up once in a template - or in software that simply won’t let you issue a document with a required field missing - rather than checking manually each time and eventually not checking at all.