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Guides / Invoicing

UK invoice numbering

Every invoice needs a unique identification number. A consistent sequence helps you find invoices, match payments and spot gaps. See GOV.UK’s invoice requirements.

Start with a simple series

Choose a format you can maintain, such as INV-001, INV-002, INV-003. You can include a year or business prefix if that helps, but keep each full number unique. The next number should come from your own records; this browser template does not store invoices or assign a sequence.

VAT invoices need a sequential number

HMRC says a full VAT invoice must have a sequential number based on one or more series that uniquely identifies the document. If you use more than one series, keep records that explain how they work. HMRC’s manual discusses numbering and gaps, including cancelled or spoiled invoices. Keep a record rather than quietly reusing a number.

A practical routine

  1. Check the last issued number in your records.
  2. Assign the next number and enter it on the invoice.
  3. Save the final PDF with that number in its filename.
  4. Record corrections or cancellations so a gap can be explained.

For the other required fields, use the UK invoice checklist.

Make the next invoice

Open the free UK invoice template and enter the next number from your own records.