An invoice is more than just a request for payment — it’s a legal document that must contain specific information under UK law. Getting your invoicing right protects your cash flow, maintains professionalism and ensures compliance.
What Must a UK Invoice Include?
A valid UK invoice must show: a unique invoice number, your business name and address, your customer’s name and address, invoice date, description of goods or services, quantity, unit price and total, VAT number and VAT amount if VAT-registered, and payment terms.
💡 Key takeaway
Limited company directors must file a personal self assessment even if their only income is a salary below the personal allowance.
VAT Invoices
If you’re VAT-registered, you must issue a VAT invoice for every sale to a VAT-registered customer. This must show your VAT registration number, the VAT rate applied and the amount of VAT charged separately. Failure to issue correct VAT invoices can result in HMRC penalties.
Invoice Numbering
Every invoice must have a unique sequential number. You can use any numbering system — starting from 001 or using date-based references like INV-2026-001. The key is that numbers must be sequential and unique — no gaps, no duplicates.
Payment Terms
Clearly state when payment is due — for example “Payment due within 30 days.” You can legally charge statutory interest on late payments under the Late Payment of Commercial Debts Act — 8% above the Bank of England base rate.
Automating Your Invoicing
Xero and QuickBooks both have professional invoicing built in — including automatic payment reminders, online payment links and recurring invoice templates. This alone can dramatically improve how quickly you get paid.
Frequently Asked Questions
Do I need to send paper invoices?
No — digital invoices are legally valid in the UK. Email invoicing is standard practice.
Can I charge interest on late invoices?
Yes — UK law allows you to charge 8% above the Bank of England base rate on business-to-business late payments.
What’s the difference between a quote and an invoice?
A quote is an estimate of cost before work is done. An invoice is a request for payment after goods or services have been provided.
