📄 Invoicing guide

How to number invoices

A consistent invoice number lets you and your client reference a specific bill, keeps your bookkeeping tidy, and is often expected (or required) for tax purposes. The good news: a simple scheme is usually best.

Try the Free Invoice GeneratorFree, no sign-up — build a PDF in minutes.

Common numbering schemes

  • Sequential — INV-0001, INV-0002, INV-0003… the simplest and most common.
  • Dated — 2026-001, 2026-002… restarting the count each year.
  • Client-based — ACME-001, ACME-002… useful if you want per-client sequences.

Rules that keep you out of trouble

  • Keep numbers unique — never reuse a number, even for a corrected invoice.
  • Keep them sequential where possible — many tax authorities expect an unbroken series.
  • Do not delete an invoice number; if you cancel one, mark it cancelled rather than reusing it.
  • Pick one scheme and stick with it — switching mid-year makes reconciliation harder.

Let the tool handle it

SafeKit suggests the next number automatically based on your last invoice, so the series stays unbroken without you tracking it by hand. You can still override the number on any individual invoice when you need to.

Frequently asked questions

Can invoice numbers include letters?
Yes. Prefixes like “INV-” or a client code are fine and often helpful. What matters is that each number is unique and the sequence is consistent.
Do invoice numbers have to start at 1?
No. You can start anywhere — some businesses start at a higher number so early invoices do not signal that the business is brand new. Just keep the series consistent from there.

Related guides