What must a UK invoice legally include

This isn't tax advice, always check current HMRC guidance or ask an accountant for your specific situation. But the baseline requirements for a UK invoice are well established and worth getting right from day one.

Required on every invoice

• A unique invoice number
• Your business name, address, and contact information
• The client's name and address
• A clear description of the goods or services provided
• The date the goods or services were supplied
• The invoice date
• The amount being charged

If you're VAT registered

You need a VAT invoice, which adds your VAT registration number, the VAT rate applied, the VAT amount, and the total including VAT. If you sell at different VAT rates within one invoice, each rate needs to be shown separately, not blended into one number.

There's also a simplified VAT invoice format for amounts under a certain threshold (check current HMRC limits, as they change), which drops some of the detail requirements. Most freelancers and small businesses invoicing for services don't need to worry about this distinction since their invoices are usually for defined, larger amounts, but it's worth knowing it exists if you're issuing a high volume of small invoices.

Sole trader specifics

If you trade under a business name that isn't your own legal name, HMRC expects your own name to appear on the invoice as well as the trading name. Plenty of sole traders miss this and only find out when a client's accounts team asks for it.

For example, if you trade as "Bright Design Studio" but you're registered as a sole trader under your own name, both should appear: "Bright Design Studio (trading name of Jane Smith)" or similar, depending on how you've set it up. This is a small detail that rarely comes up until a client's finance team specifically flags it, at which point it's better to already have it right than to scramble to reissue an invoice.

What's optional but worth including anyway

• Payment terms and a specific due date, which aren't strictly a legal requirement but massively reduce late payment.
• Your bank details or a payment link, so the client doesn't need to email you separately to ask how to pay.
• A purchase order (PO) number if the client gave you one, since many corporate accounts payable systems won't process an invoice without it.
• Your company registration number if you operate as a limited company, even though this is more relevant to the next section.

Limited company invoices

If you invoice through a limited company rather than as a sole trader, the invoice should show your full registered company name exactly as it appears at Companies House, plus your company registration number. Many limited companies also include their registered office address on invoices, even if their trading address is different, since this is what appears on official documents.

invoiceKit doesn't calculate VAT for you automatically by jurisdiction, since VAT rules vary and change, but it does let you add a tax percentage and it will calculate and display the tax amount and total clearly on every invoice.