How to Write an Invoice (UK Guide) + Free Template

If you're self-employed, running a small business, or freelancing in the UK, sending a proper invoice isn't optional — it's how you actually get paid on time, and in some cases it's a legal requirement. This guide walks through what an invoice is, exactly what needs to be on it under UK rules, and how to write one in minutes using a free template.

What Is an Invoice?

An invoice is a document you send to a customer or client requesting payment for goods or services you've provided. It's different from a receipt (which confirms payment already made) and different from a quote or estimate (which is sent before work starts, not after). An invoice is your formal, dated record that says: here's what I did, here's what it costs, and here's how and when to pay me.

Invoices matter for three reasons:

• They're your proof of what was agreed and delivered, if a dispute ever comes up
• They're needed for your own bookkeeping and tax records
• If you're VAT-registered, HMRC requires specific invoice details by law

What Legally Has to Be on a UK Invoice

If you're a sole trader, limited company, or VAT-registered business in the UK, your invoice needs to include:

Limited Company Requirement: If you're a limited company, you also need to include the full company name as it appears on the certificate of incorporation, and if you list any directors' names, you must list all of them.

How to Write an Invoice — Step by Step

1. Add a unique invoice number. Sequential numbering (INV-001, INV-002...) keeps your records clean and makes VAT returns easier.
2. Add your business details. Name, address, phone, email — and VAT number if registered.
3. Add the customer's details. Full name/business name and billing address.
4. Describe the work clearly. Line items with quantity, rate, and total — vague descriptions cause payment delays.
5. State the invoice date and due date. UK standard payment terms are usually 30 days, but you can set your own (e.g. 14 days).
6. Add up the total, including VAT if applicable.
7. Include your payment details. Bank details, or a payment link, so there's no back-and-forth.
8. Send it promptly. The sooner it goes out after the work is done, the sooner you get paid.

How to Send an Invoice

Once it's written, sending it is simple:

• Email is the standard method — attach as a PDF so formatting doesn't break, and use a clear subject line like "Invoice #INV-014 from [Your Business]"
• Invoicing software (like InvoiceBolt) lets you generate and download a ready-to-send PDF in one step, with no manual formatting
• Post is still valid for clients who require paper copies, though this is increasingly rare

Whichever method you use, keep a copy for your own records — HMRC generally expects businesses to keep invoice records for at least 6 years.

Free UK Invoice Template

You don't need to build an invoice from scratch in a spreadsheet every time. InvoiceBolt gives you a free, ready-made UK invoice template — just fill in your details, add your line items, and download a clean PDF. It includes all the legally required fields above, works offline, and there's no sign-up needed.

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