How to Write an Invoice in the UK: A Step-by-Step Guide

Writing an invoice sounds simple until you’re staring at a blank page wondering what actually needs to be on it. UK invoices don’t require a fixed template by law, but there is a standard set of information clients, accountants and HMRC all expect to see — and leaving it out is the most common reason payments get delayed.

1. A unique invoice number

Every invoice needs its own reference, usually sequential (INV-0001, INV-0002, and so on). This matters more than it sounds: it’s how you and your client track which invoice a payment relates to, and how you’ll find a specific invoice again months later.

2. Your details and your client’s details

Include your name or business name and address, and the same for your client. If you trade as a limited company, add your company registration number; if you’re VAT registered, your VAT number goes here too (or in a clearly labelled VAT section).

3. The invoice date and due date

The issue date starts the clock on your payment terms. State the due date explicitly rather than leaving it implied — “payment due within 30 days” is far less likely to be missed than a date with no explanation.

4. A clear description of the work or goods

Vague line items like “Services” invite questions and slow down payment. “Website redesign — homepage and 3 inner pages” tells the client exactly what they’re paying for, and gives you a paper trail if there’s ever a dispute.

5. The amount, and VAT if it applies

Show the subtotal, any VAT (if you’re VAT registered) at the correct rate, and the grand total. If you’re not VAT registered, simply don’t include a VAT line — you’re not legally allowed to charge VAT unless you’re registered, so don’t estimate one “just in case”.

6. Payment terms and how to pay

State your payment terms (e.g. Net 30) and how you’d like to be paid — bank transfer details are the norm for most UK small businesses. The clearer this is, the fewer follow-up emails you’ll need to send.

Putting it together

In practice, all six of these fit naturally onto a single page: your details and your client’s details side by side near the top, the invoice number and dates in a small table, your line items in the middle, and the totals and payment terms at the bottom. That’s exactly the layout our free UK invoice generator uses, so you don’t have to design one from scratch — just fill in the fields and download the PDF.