What has to be on a sole trader's invoice?

Two kinds of invoice, and which one is yours

Australia distinguishes a plain invoice from a tax invoice. A tax invoice is the GST document — only businesses registered for GST issue them, and their customers need them to claim GST credits. If you're not registered for GST, you issue ordinary invoices, and the rules are actually stricter about what you must NOT include.

If you're registered for GST

For sales of $82.50 or more (including GST), your customer is entitled to a tax invoice, and you must provide one within 28 days if they ask. It needs: the words 'Tax invoice', your identity (business or trading name), your ABN, the date, a description of what was sold including quantity and price, the GST amount (or a statement that the total includes GST), and — for invoices of $1,000 or more — the buyer's identity or ABN too.

If you're NOT registered for GST

Your invoices must not say 'Tax invoice', and you must not add GST to your prices — charging GST while unregistered is unlawful. A clean layout is: your name and ABN, the word 'Invoice', the date, what was sold, and the amount. Many businesses also add 'No GST has been charged' so customers' bookkeepers don't come asking for a tax invoice.

Either way, an ABN matters: without one on your invoice, business customers may be required to withhold 47% of the payment under the no-ABN withholding rules.

What makes an invoice get paid

Beyond the legal fields, the practical ones: a due date stated as a date rather than '14 days', your bank details exactly once, a reference the customer recognises (their job, their PO), and a number you can chase it by. Send it the day the work finishes — invoice age is the single strongest predictor of how long payment takes.