The minimum requirements stipulate an invoice must include:

• If you are a sole trader or partnership, your name and any business name being used,
• an address where any legal documents can be delivered to you,
• a unique identification number, usually a sales invoice number,
• your business name, address and contact information, such as telephone number and/or e-mail address,
• our company name and address,
• a clear description of what you are charging for,
• the date the goods or service were provided (supply date) if different to the invoice date,
• the date of the invoice,
• the amount(s) being charged,
• VAT amount if applicable,
• the total amount owed,
• if you are a sole trader or partnership please also supply your UTR number.

if VAT is charged you must also ensure your invoice includes:

• your VAT number,
• the rate of VAT charged.

If your business is a limited company, you must also include:

• the full company name as it appears on the certificate of incorporation,
• the company registration number and place of registration, for example, England and Wales.

Guidance on the requirement for invoices can be found at:
https://www.gov.uk/invoicing-and-taking-payment-from-customers/invoices-what-they-must-include