To cancel a shipping label you just need to click the three dots next to the order and select "Cancel Shipping Label".
This will cancel the shipping label in our system so that you can purchase more postage for the order.
If you cancel a shipping label then the funds will be automatically returned to your Shipping Balance in 7 days.
If you just need to repurchase a shipping label for an order check out this article for more directions.
If the status of the order is "In Transit" you will not be able to cancel the shipping label this way.