All sellers are required to provide Amazon Business customers with a correct and valid VAT invoice for each order promptly after the shipment of the order was confirmed, except the situation that seller cannot find the "Contact buyer" link on manage order detail page. Amazon offers sellers the opportunity to create invoices via the Amazon VAT Calculation Service, in which case the invoice is automatically available for download in the customer account. In case sellers are not using the Amazon VAT Calculation Service, the invoice must be sent to the customer email address provided in the order details in PDF format, using the Amazon Buyer-Seller Messaging system.
If you are not required to apply VAT on your sales, you are still required to provide a receipt for each order from an Amazon Business customer.
Failure to comply can result in actions taken against your selling account.
For more information, please refer to this help page.