A commercial invoice is a document containing important information about the goods you intend to ship; they're also used to create a customs declaration.
What must they include?
Your invoice must include:
What happens if I do not have a Commercial Invoice or fail to fill it out accurately?
A Commercial Invoice is an obligatory document that must be created in order to import or export any goods in the UK. Inaccuracies on a commercial invoice can and will lead to errors regarding duties and taxes which could, in turn, result in delays, fines and further legal implications.
Per https://www.gov.uk/invoicing-and-taking-payment-from-customers/invoices-what-they-must-include https://www.ups.com/gb/en/help-center/packaging-and-supplies/export/comm-invoice.page