A payment can be cancelled while it is in "Pending" status.  A "Cancel" link is available to the far right of any pending payment that will allow you cancel it.  Click it and a dialog will ask you to confirm.  Once confirmed, the payment will disappear from the order.

*Payments with a "Completed" status cannot be cancelled, regardless of what payment method was used. Refer to the Refunding Payments solution to learn how to refund any completed payments.

Cancelling Scheduled Credit Card Payments

A credit card payment that is scheduled to be automatically processed by your credit card provider is listed as status: pending. This can be stopped by clicking "Cancel" to the far right of that payment from the order page.

After confirming, it will automatically communicate with your payment provider and cancel the scheduled payment.  The payment will then disappear from the order. Payments that you cancel this way will be cancelled permanently.

*No further action is required with the payment provider. The payment will be cancelled with them automatically when cancelling in the HCR.

You can log in to your payment provider console to verify that the cancellation was processed successfully.