All sellers are required to provide Amazon Business customers with a valid VAT invoice for each order within one business day after order dispatch is confirmed. Sellers that are not required to apply VAT on their sales are required to provide receipts. Similarly, credit notes on returns from Amazon Business customers must be provided within one business day of return confirmation.
Amazon allows sellers to provide invoices and credit notes via the Amazon VAT Calculation Service, in which case invoices and credit notes are either generated by Amazon, or generated by the seller based on VAT calculation data provided by Amazon (available for eligible third-party solution providers only). Sellers that do not use the Amazon VAT Calculation Service must upload invoices and credit notes, either on Seller Central via Manage Orders or using a third-party solution provider.
Sellers not required to apply VAT on their sales still have to provide a receipt for each order from an Amazon Business customer.
For more information, please refer to this help page.