You can cancel an order while the status is pending.
Orders are listed as Pending while Amazon is trying to verify the payment method provided by the buyer. Pending orders will not include the buyer's address for shipping, or contact information, and should not be shipped, even if the buyer contacts you directly.
An order with a status of Pending may indicate an issue with the buyer's payment method, for example, the convenient store payment has not been completed yet.
Once the payment method is verified successfully, the Confirm shipment button will appear in Manage Orders and the order will appear in both the Orders Report and the Unshipped Orders Report. At that point, the order should be fulfilled (or canceled if necessary). Amazon assumes the risk of buyer non-payment for every order in your Unshipped Orders Report or that has Confirm shipment and Cancel order buttons in Manage Orders. Of course, there may still be circumstances where payment may later need to be refunded, for example when the buyer does not receive the order, or it is not as described.
Here are some of the most common reasons for orders being in Pending status.