Free Invoice Generator

Invoice number generator

Choose a prefix, whether the year goes in, and how many digits the count has. The sheet lists the next invoice numbers and warns you about anything that will cause trouble later, such as repeats, numbers that sort out of order, or characters that break file names.

The format

Leave it blank for numbers like 2026-001.

The guide recommends leaving this out. The notes below say why.

The count

1 for a new sequence. If you already have invoices, the one after your last.

Used only to check that the count has enough digits.

The list

Today, unless you are setting up for later. Sets the year and month.

GuideInvoice numberingHow this works, and where the figures go wrong →

What the sheet checks

  • Numbers that would repeat. A count that restarts every January needs the year in the number, or next January's first invoice has the same number as this January's. This is the only warning that makes a scheme unusable rather than awkward.
  • Numbers that sort out of order. Files, spreadsheets and email searches sort numbers as text, character by character, so INV-1000 lands between INV-100 and INV-101. Padding the count with zeros keeps every number the same length, which keeps them in order. The sheet warns when the list, or the number of invoices you expect in a year, needs more digits than you have chosen. If the count never restarts, it warns when the digits would run out within 5 years.
  • Characters that travel badly. Spaces, slashes, accented letters and other symbols get mangled in file names and URLs, and some payment reference fields drop or refuse them. Letters, digits, hyphens and underscores are safe.
  • Numbers that are hard to read out. Over 16 characters, or with no separator between the year and the count. That limit is our judgement, not a rule: the number gets spoken on calls and typed into remittances, and each extra character is another chance of a typing mistake.

Why the guide leaves the client out

A client code makes numbers like ACME-2026-004 that look organised and sort by client in a folder. The invoice numbering guide recommends against it for three reasons: a sequence per client means you can no longer see a missing invoice at a glance, clients rename and get bought, and the number tells the client things about your business that you may not mean to share. This generator keeps one count across every client even when you add a code, so the next client's invoice takes the next number.

Restart every year, or never

Both work. 2026-001 restarting each January tells you at a glance how many invoices you sent in a year. A single count that never restarts is shorter. What causes trouble is switching from one to the other halfway through, so pick one before the first invoice. In the UK, HMRC's VAT Notice 700, section 16.3.1, asks VAT invoices to carry "a sequential number based on one or more series which uniquely identifies the document". Other countries have their own rules, so check the tax authority's guidance where you are registered.

What this generator does not do

  • It does not keep count for you. It does not know your last invoice number and will not remember the next one. Type the next number in the count each time, or keep it in whatever you use for your records.
  • It does not fix a gap. If you cancel an invoice, do not reuse its number. The guide explains how to issue the replacement, and when a credit note is the right way to cancel the original.
  • It does not keep anything. Nothing is written to your browser's storage and nothing you type is sent to us.

Related

Once you have a format, the invoice generator takes the number in its Invoice number field. What to put on an invoice covers the other fields, and the payment terms generator writes the terms line that goes under them.

Last updated 3 October 2026