An invoice is a document you send a customer asking them to pay for goods or services you have supplied. It records what was supplied, how much is owed, and when payment is due. In Australia there is no law setting out what a plain invoice must contain — but the moment you are registered for GST, the same document has to meet the ATO's requirements for a tax invoice, and your ABN has to be on it either way.
What an invoice is for
Three jobs, and it is worth being clear about them because they explain every field on the page:
- It asks for money. An invoice creates a debt. Until you issue one, in most arrangements there is nothing legally owing and nothing to chase.
- It is your record of the sale. Your income, your GST, and the figures you report on your BAS and tax return all trace back to invoices.
- It is your customer's evidence. They need it to claim the expense as a deduction, and — if the sale carried GST — to claim the GST credit.
What goes on an Australian invoice
Nothing in Australian law prescribes the contents of a plain invoice, so this list is common practice rather than a legal minimum. Leave any of it out and you make it easier for the customer to delay.
| Part | Why it matters |
|---|---|
| The word "Invoice" | So nobody mistakes it for a quote, a statement or a reminder. If you are registered for GST it says "Tax invoice" instead. |
| Your business name and ABN | Without the ABN the payer must withhold tax at the top rate. The business name should match what is on the register. |
| The customer’s name | And their ABN once the sale is $1,000 or more, if the document is a tax invoice. |
| A unique invoice number | How both of you refer to this sale for the next five years. Sequential, never reused. |
| The issue date | Payment terms run from here, so it is the date the clock starts. |
| A description of what was supplied | Quantity, unit price and line total. Vague descriptions are the most common reason an invoice is queried rather than paid. |
| The total, and the GST if any | Show the GST amount separately, or state that the total includes GST. Never show GST if you are not registered for it. |
| Payment terms and due date | "Net 14" means nothing to some customers. Print the actual date. |
| How to pay | BSB and account number, PayID, or a payment link. On the invoice itself, not only in the email. |
When does an invoice have to be a tax invoice?
If you are registered for GST and the sale is a taxable sale, your customer needs a valid tax invoice to claim the GST credit on any purchase over $82.50 including GST. A tax invoice has seven required elements and must be issued within 28 days of a request. If you are not registered for GST, you must not label a document a tax invoice and must not show a GST amount — there is no GST in your price to show.
The full requirements, and how to calculate the GST line correctly, are on how to invoice with GST. If you are not sure whether you should be registered at all, start with do I need to register for GST?
Why your ABN has to be on it
When one business pays another and the invoice does not quote an ABN, the payer is generally required to withhold tax at the top rate and send it to the ATO. You get it back when you lodge your return, but you are short most of the payment until then. Put your ABN on every invoice, including the ones to friends and the ones for $80. See how to get an ABN if you do not have one yet.
How to number invoices
Invoice numbers are the spine of your records, and the rules are simple enough that there is no excuse for getting them wrong:
- Unique, always. No number is ever used twice, even across years.
- Sequential, with no gaps. A gap invites the question of what was in it. If you void an invoice, keep the number and mark it cancelled rather than deleting it.
- Never renumber an invoice you have already sent. If it was wrong, issue a credit note and a fresh invoice.
- Keep the format boring. INV-0001 or 2026-0001 both work. A per-client prefix looks tidy and makes it much harder to prove your numbering is complete.
- Do not start at 1 if you would rather not advertise that this is your first invoice. Starting at 1001 is common and entirely legitimate.
Keep proforma invoices and quotes out of the invoice sequence — they are not invoices, and mixing them in is what creates gaps.
How to send an invoice
Email a PDF. That is the normal method in Australia, it is legally effective, and it timestamps itself. A few things that measurably shorten the time to payment:
- Send it the day the work finishes, not at the end of the month. Payment terms start from the invoice date, so a week's delay in sending is a week's delay in being paid.
- Put the payment details on the invoice itself, not in the covering email. The invoice is what gets forwarded to accounts payable; the email often is not.
- Ask a corporate or government client for a purchase order number before you start, and quote it on the invoice. Without it their system may not be able to match the invoice, and it will sit unpaid without anyone deciding not to pay it — see what is a purchase order?
- Name the file usefully — INV-0042-YourBusiness.pdf beats invoice.pdf in a mailbox with two hundred of them.
Everything about terms, reminders and chasing is in how to get paid on time.
Documents that are not invoices
| Document | How it differs |
|---|---|
| Quote or estimate | An offer to do work at a price. Creates no debt, and nothing is owed if the customer walks away. |
| Proforma invoice | Invoice-shaped, but a request for payment in advance rather than a record of a completed supply. Not a tax invoice, and no GST credit can be claimed from it. |
| Purchase order | Issued by the buyer, not you. It commits them to buy; your invoice comes afterwards and asks to be paid. |
| Receipt | Confirms money was received. Issued after payment, by you, and it is the customer’s proof rather than yours. |
| Statement of account | A summary of everything invoiced, paid and outstanding over a period. A reminder, not a new debt. |
How long to keep them
Five years. The ATO requires records that explain your transactions to be kept for five years from the date the record was prepared or obtained, or the transaction was completed — whichever is latest. Digital copies are fine, provided they are complete, legible and can be produced on request. A folder per financial year is enough structure for one person.
Related reading
- How to invoice with GST — the seven elements of a valid tax invoice
- Invoice vs receipt — which one proves payment
- What is a proforma invoice? — the one that is not a demand for payment
- How to get paid on time — terms, deposits and reminders
Frequently asked questions
An invoice is not a contract, but it is a legally significant record — it evidences the debt, it is the basis of your reported income, and it is the document a court or the ATO will look at. There is no law prescribing what a plain invoice must contain, but a tax invoice issued by a GST-registered business has seven required elements set by the ATO.
You can issue the document, but the business paying you is generally required to withhold tax at the top rate and send it to the ATO, so you receive roughly half the money until you lodge your return. Applying for an ABN through abr.gov.au is free and usually immediate, so there is rarely a good reason to invoice without one.
Only if you are registered for GST. Registration is compulsory once your GST turnover reaches $75,000 over a rolling twelve months, and optional below that. If you are not registered you must not show a GST amount and must not call the document a tax invoice — charging GST you are not entitled to collect is a real problem, not a paperwork one.
The day the work is finished, or at the agreed milestone. Payment terms run from the invoice date, so every day you delay sending is a day added to when you get paid. If you are registered for GST and a customer asks for a tax invoice, you must provide it within 28 days of the request.
No. Once an invoice has gone out it is part of your records and part of your customer’s. If it was wrong, issue a credit note reversing it and then issue a corrected invoice with a new number. Editing or deleting breaks the audit trail, and a gap in your numbering is exactly what a reviewer asks about.
Sources
Tax invoice requirements, the $82.50 threshold, no-ABN withholding and the five-year record-keeping rule come from the Australian Taxation Office; general invoicing practice from business.gov.au. Confirm the current position at ato.gov.au or with a registered tax agent. Balaana is bookkeeping software, not a tax agent — this article is general information, not personal tax advice.