Depending on the payment gateway you use, you may be able to void authorizations.
To void an authorization:
In the list of payments on the Payments page, locate the payment for which you want to void an authorization and open its details for viewing.
On the Payment details page, locate the section for Capture/Void actions:
The payment will be declined:
Note that once authorization has been voided, you will no longer be able to capture the payment - it will be declined.