You can cancel any unshipped items or orders from your Manage orders page. After you cancel an item or order, Amazon will send a cancellation email to the buyer.
Cancel one order or items within an order
On the Manage Orders page, locate the order you want to cancel.
Click Cancel Order in the Action column.
Select from Cancel entire order or Cancel items.
For Cancel items, select the ASIN and quantity you wish to cancel.
On the Cancel Order page, select a Reason for Cancellation. You may also enter any information you want to keep track of in the Seller memo field.
Cancel multiple orders
You can also cancel multiple orders using one of the following techniques:
We expect sellers to maintain accurate inventory levels. Failure to adjust your inventory in a timely manner can lead to excessive pre-fulfillment order cancellations. For information on how we factor cancelled orders into your overall performance, see Customer Metrics
Important: You must be an Amazon MWS developer in order to send a Feeds request.
Occasionally, you may need to cancel part of an order with multiple items and refund the items that are cancelled. If you manage your orders using inventory files, you can upload an Order Adjustment Feed.
To cancel or refund part of a multi-item order, follow these steps:
Ship and confirm all the order items that you can fulfill.
Use an Order Adjustment Feed to submit a refund for the order items that you cannot fulfill. Provide the following information in the feed:
Quantity Cancelled: The quantity that cannot be fulfilled.
Adjustment Reason: The refund code. Select either NoInventory or CustomerCancel.
For more information, see Refund or Partially Cancel Orders—Order Adjustment or Partial Cancellation.