A unique reference number (in case of correspondence about the invoice)
Date of the invoice
Name and contact details of the seller
Tax or company registration details of seller (if relevant)
Name and contact details of the buyer
Date that the product was sent or delivered
Purchase order number (or similar tracking numbers requested by the buyer to be mentioned on the invoice)
Description of the product(s)
Unit price(s) of the product(s) (if relevant)
Total amount charged (optionally with breakdown of taxes, if relevant)
Payment terms (including method of payment, date of payment, and details about charges late payment)
The US Defense Logistics Agency requires an employer identification number on invoices.
The European Union requires a VAT (value added tax) identification number on invoices between entities registered for VAT.
If seller and buyer belong to two different EU countries, both VAT identification numbers must be on the invoice in order to claim VAT exemption (VAT exemption according to directive 77/388/CEE of 17 May 1977).
In the UK, if the issuing entity is not registered for VAT, the invoice must state that it is "not a VAT invoice".
