A system and method for the use of ultra high frequency RFID tags in conjunction with metal substrates, as well as substrates used to contain liquid. Briefly, an RFID isolator comprised of a material with complex magnetic permeability, used either by itself, or in combination with dielectric isolator material, is interposed between the RFID tag and the substrate. Alternatively, a material possessing at least two distinct dielectric constants is interposed between the RFID tag and the substrate, such that there is a high dielectric constant at the interface with the substrate, and a low dielectric constant at the interface with the RFID tag. This material can be a single material having a dielectric constant gradient, or alternatively, two or more separate layers, each with a uniform but different dielectric constant, sandwiched together.