We will not process a refund on packages marked as Return to Sender. Rejecting receipt of a package (a.k.a., "Return to Sender", or "RTS") is considered returning the package without an RMA Number and may be charged up to 50% of the retail value as a restocking fee. Any fees or shipping charges incurred by the unauthorized return of the package will be re-billed to the customer in the form of a deduction from any applicable refund amount. In cases where the rejected package costs more than the order itself, a refund is not possible. Any shipping and/or customs charges billed to a Stackit shipping account and not explicitly authorized by Stackit will be billed to the customer. Stackit is not responsible for invalid shipping addresses; we will ship to the address you provide on your order. Stackit is also not responsible for a customers’ failure to respond to a carriers’ pickup instructions. Undeliverable orders will either be Returned to Sender or destroyed by the ground carrier and will NOT be replaced nor refunded.