Invoice number one. Do you really send a bill with #1 on it and tell the world you started last Tuesday? And what happens when you delete one, or the numbers drift out of order? Small thing, but messy numbering causes real headaches later.
The three rules
- Every invoice gets its own number. No repeats, ever.
- Numbers go up in sequence. 14 comes after 13.
- Never delete an invoice from the sequence. If one was a mistake, cancel or void it and keep the number. A gap with no explanation looks like a missing sale.
That's it. Everything else is preference.
Formats that work
- Plain sequence: 1, 2, 3. Simple, never breaks.
- Year prefix: 2026-014. Resets each year, and you can see the year at a glance.
- Prefix by type: INV-014 for invoices, Q-014 for quotes, so nobody confuses a quote with a bill.
Pick one and stay with it. Switching formats mid-year is how sequences get tangled.
Can you start at 1000?
Yes. Nothing says the first invoice must be #1. Plenty of sole traders start at 1000 or 0101 so the business doesn't look brand new. The rules care that numbers are unique and sequential from wherever you start, not where you start.
Why it matters more than it looks
Your invoice numbers are the backbone of your records. When you do your BAS or hand a year to your accountant, a clean sequence proves every sale is accounted for. When you chase a payment, "invoice 2026-014" removes any argument about which bill you mean. And if the ATO ever looks at your books, unexplained gaps and duplicates are exactly the kind of thing that turns a quick look into a long one.
Two minutes of system now saves hours of archaeology later.
Never think about invoice numbers again
UteHQ numbers every quote, job and invoice automatically, in sequence, no repeats. Free, unlimited.
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