The label has to be cancelled within 5 days
If you haven't used a postage label, you can cancel it within 5 days of creating and
printing the label.Under the Manage postage labels section of My eBay, select the Cancel postage label option.
If your cancellation request is approved, you'll receive a credit for postage and related charges within 25 days. The credit will be shown on your Seller Account, and on the following eBay monthly invoice.
Note:
If the label didn't print correctly, you don't need to cancel it - you can reprint it within 24 hours.
You may not use a label after it's been cancelled, or cancel a label after you've dropped the package off.
http://pages.ebay.com.au/help/pay/printing-labels.html#cancel
