UK VAT invoice requirements

If you are VAT-registered in the UK, a full VAT invoice must contain a specific set of fields so your customer can reclaim VAT. A simplified invoice (fewer fields) is allowed when the total is £250 or less, and invoices should generally be issued within 30 days of the supply.

• A unique, sequential invoice number
• Your business name, address and VAT registration number
• The invoice date, and the time of supply ("tax point") if different
• The customer's name and address
• A description of the goods or services supplied
• For each item: quantity, unit price excluding VAT, the VAT rate, and the amount excluding VAT
• The rate of any cash/settlement discount
• The total amount excluding VAT, the total VAT, and the total payable including VAT

Verified against gov.uk (VAT record keeping / VAT invoices). Always confirm current HMRC guidance for your situation.

Official source: gov.uk: VAT invoices