An invoice is not just a polite request for payment. It is a legal document, and getting the required details wrong can block your customer from reclaiming VAT, expose your business to HMRC penalties of up to £3,000 for inadequate records, and create genuine headaches during an audit. Fortunately, the core requirements are straightforward once you know exactly what needs to appear on every invoice you send.
This guide covers how to write an invoice in the UK, the legal requirements for different business types, and how to protect yourself against invoice fraud.
What Every UK Invoice Must Include
Regardless of business structure or VAT status, HMRC expects every invoice to contain a core set of information: a unique, sequential invoice number, the invoice date, your business name and address, the customer’s name and address, a clear description of the goods or services supplied, the date of supply, the amount charged, and the total owed. Missing any of these creates problems if a customer later disputes payment or if HMRC ever reviews your records.
Requirements That Differ by Business Structure
Sole Traders
If you trade as a sole trader, your invoice needs your own name, plus your trading name if it differs, and a UK business address where legal documents can be served.
Limited Companies
A compliant limited company invoice must include your full registered company name exactly as it appears at Companies House, your company registration number, and your registered office address, requirements that sit on top of the basic invoice details and stem directly from the Companies Act 2006. If you have recently registered a company, these details should already be to hand from your incorporation paperwork.
VAT Invoices: The Additional Requirements
If your business is VAT-registered, invoices issued to other VAT-registered businesses must additionally show your VAT registration number, the VAT rate applied, the VAT amount charged, and the net amount before VAT. Omitting these details means your customer cannot reclaim the VAT they have paid, which can quickly damage a business relationship even when the underlying transaction was straightforward.
Setting Up a Numbering System
Every invoice number must be unique and should follow a sequential system, never reused, so that both you and HMRC can track it clearly against your financial records. A simple structure combining a customer code with a sequential number, such as CLIENTCODE-001, works well for businesses invoicing multiple regular customers, and credit notes issued to correct a previous invoice must also carry their own unique number that clearly references the original.
Payment Terms and Bank Details
Clearly state your payment terms, including the due date and any late payment charges that apply. While including bank details is not a strict legal requirement, most customers will not pay without them, so it is worth including your account details for BACS or Faster Payments, along with a clear payment reference asking customers to quote the invoice number.
Protecting Against Invoice Fraud
Invoice fraud, where criminals intercept an invoice and quietly replace the supplier’s bank details with their own, is a genuine and growing risk. Adding a simple note such as confirming your bank details will never change without a verified phone call, and encouraging customers to call and confirm before acting on any unexpected change request, is a small step that can prevent a serious financial loss.
Record-Keeping Requirements
HMRC requires businesses to keep copies of invoices, both issued and received, for at least six years, forming part of your broader tax record-keeping obligations. Using accounting software rather than a folder of loose paper invoices makes this considerably easier to manage, particularly once volumes grow.
Comparing Invoice Requirements by Business Type
| Requirement | Sole Trader | Limited Company | VAT-Registered |
|---|---|---|---|
| Unique invoice number | Required | Required | Required |
| Company registration number | Not applicable | Required | Required if a company |
| VAT registration number | Only if VAT-registered | Only if VAT-registered | Required |
| Registered office address | Not applicable | Required | Required if a company |
| Six-year record retention | Required | Required | Required |
Common Invoicing Mistakes to Avoid
- Reusing invoice numbers or skipping a sequential system entirely
- Omitting VAT details when invoicing another VAT-registered business
- Leaving out the company registration number on a limited company invoice
- Failing to state clear payment terms and due dates
- Not verifying bank detail change requests, leaving the business exposed to invoice fraud
Frequently Asked Questions
Do I legally need to include bank details on an invoice?
No, it is not a strict legal requirement, but most customers expect to see them and are unlikely to pay promptly without clear payment instructions.
How long must UK businesses keep invoice records?
HMRC requires invoices and related financial records to be kept for at least six years, whether stored digitally or on paper.
Is a receipt the same as an invoice?
No. An invoice is a request for payment issued before or alongside delivery of goods or services, while a receipt is proof that payment has already been received, and is good practice rather than a strict legal requirement.
What happens if my invoice is missing required VAT details?
Your VAT-registered customer will not be able to reclaim the VAT they have paid, which can create friction in the business relationship even where the transaction itself was otherwise straightforward.
Final Thoughts
Writing a compliant UK invoice is largely a matter of including a consistent, complete set of details every time: a unique number, accurate business and customer information, clear VAT treatment where relevant, and defined payment terms. Building this into a template or your accounting software from the outset protects your business legally and helps you get paid faster and with fewer disputes.
