Getting paid starts with sending an invoice that has the right information on it. That sounds basic, but plenty of UK businesses send out invoices missing legal requirements, which can cause delays, disputes, and in some cases, complications with HMRC.
What UK law requires on an invoice
If your business is a limited company, your invoice must include your registered company name, your Companies House registration number, your registered office address (which might be different to where you actually work), and the names of any directors listed on your registration.
For sole traders, you need your real name even if you trade under a different name. So if you're trading as Bright Digital but your name is Sarah Clarke, the invoice needs to say Sarah Clarke trading as Bright Digital.
Every business, regardless of structure, needs a unique invoice number, the date the invoice was issued, a clear description of what you're charging for, the amount due, and your payment terms.
If you're VAT registered, you must also include your VAT registration number, show the VAT amount separately, and state the VAT rate charged. An invoice missing any of these is not a valid VAT invoice, which can cause problems for clients trying to reclaim input tax.
Invoice numbering and why it matters
Your invoice numbers need to be sequential and unique. INV-001, INV-002, and so on. HMRC can check for gaps in numbering during investigations, so if you go from INV-045 to INV-048, you'll need to explain why.
A date-based format like 2025-001 works fine. What you can't do is reuse numbers or issue the same number twice, even if the original invoice was cancelled.
Setting clear payment terms
Payment on receipt is vague and creates disputes. State specific terms: 30 days from invoice date, due by the 15th of the following month, whatever arrangement you have. And make sure you've agreed these with the client before you do the work, not after.
UK law under the Late Payment of Commercial Debts Act gives you the right to charge interest on overdue invoices, currently set at 8% above the Bank of England base rate. You don't have to enforce it, but including a note on your invoice that late payments may incur interest does tend to focus minds.
What to do when someone does not pay
Send a reminder before the due date. Most late payments aren't deliberate; they get lost in accounts payable queues. A brief email a few days before the due date catches a lot of problems early.
After the due date, be direct. Send a formal overdue notice with the invoice attached again. If that doesn't work within a few weeks, a statutory demand is a formal legal step that can trigger serious consequences for incorporated clients, which tends to result in payment.
Digital invoicing and record keeping
Under Making Tax Digital, most businesses are now required to keep digital records of their income and expenses. That means storing invoices electronically, not in a filing cabinet.
Using invoicing software, like the invoicing module in WeekOne, handles the numbering, VAT calculations, client records, and payment reminders automatically. It also means every invoice is searchable and ready for your accountant at year end without any scrambling.
Common mistakes worth avoiding
- Sending to the wrong email address or the wrong person in accounts payable
- Not including your bank details (sort code, account number, or a payment link)
- Using the wrong VAT rate for the goods or services provided
- Forgetting to attach the invoice to the email
- Incorrect or missing invoice date
These feel minor but any of them can delay payment by weeks. A proper invoice template with required fields locked in means you don't have to think about it each time.