RxLink determines the most efficient shipping and delivery carrier for your order. The carriers that may be used are: U.S. Postal Service (USPS), United Parcel Service (UPS) or FedEx. Sorry but we cannot ship to P.O.Boxes. If you are trying to estimate when a package will be delivered, please note the following: Credit card authorization and verification must be received prior to processing. Please contact RxLink at 1-855-679-5465 with any questions. Please note: Out of state orders will not be charged sales tax. In state orders will be charged 5% sales tax.