Invoice number generator

Two ways to use it: paste your last invoice number to get the next one, or design a format and generate a run of numbers.

Everything runs in your browser. Nothing you type is sent anywhere or saved.

1. What's my next invoice number?

Unique and in order. Each invoice gets one number that's never reused. If you void an invoice, keep its number and mark it void rather than reusing it.
Padding keeps lists sorted. INV-0009 sorts before INV-0010 in a spreadsheet or folder; INV-9 and INV-10 don't.
A year or financial-year part makes old invoices easy to find, but you can keep counting across years (simplest) or restart at 0001 each year. Pick one and stick with it.
Ask customers to quote it as the payment reference, so bank deposits match invoices.
Is a number required? The ATO's list of what a tax invoice must show (for sales under $1,000: that it's a tax invoice, your identity and ABN, the issue date, what was sold with quantity and price, the GST, and how much of each sale is taxable; plus the buyer's identity or ABN from $1,000) doesn't include an invoice number. It's still standard practice, and the reminder emails in our free tools quote it.

Source (checked 17 Oct 2026): ATO Tax invoices (updated 18 Sep 2026).

General information, not tax advice.