Open the card and click Cancel Card. The button is only offered while the card's status is Active. Clicking it changes the status to Cancelled, the page records who cancelled it and when ("Status changed to Cancelled by … on …"), and the code can no longer be redeemed ("This Gift Card code was canceled."). Cancellation cannot be undone from the admin, and it does not refund the buyer or reverse any wallet credit already given — handle any refund on the original order.

Note: refunding the order that purchased the gift card (from Checkouts) also cancels the card automatically as part of that refund.

Note: because of the status-field quirk described in the redemption question, Cancel Card can still be offered on a card a customer has already redeemed at checkout (it will still show Active). Cancelling it at that point only marks the record Cancelled going forward — the wallet credit the customer already received is not reversed.