Each voucher is subject to its own list of valid redemption locations/qualifying merchants or categories as displayed on the voucher activation webpage. You can always refer to the list of valid redemption locations in the email sent to you upon activating your voucher by clicking "View Voucher Detail" in the email body. Your voucher can only be redeemed in-store unless otherwise specified in the merchant list.
Please note you will only receive a statement credit if you make a qualifying purchase at a qualifying merchant location or a qualifying merchant category.