There is no need to inform the Buyer that the order is done.
The Buyer will receive automatically a notification message update that the order is done on the order page. Additionally, the Buyer will receive automatically an email stating that the order is done.
An order is successfully completed when the Buyer has approved the purchased product or service. The Buyer still has the possibility at this stage to decline the order. The Seller is then requested to provide an update for services or work out a solution to ensure the Buyer receives the products as requested.