High Quality Content by WIKIPEDIA articles! A NERC Tag, also commonly referred to as an E-Tag, represents a transaction on the North American bulk electricity market scheduled to flow within, between or across electric utility company territories. The NERC Tag is named for the North American Electric Reliability Corporation (NERC), which is the entity that was responsible for the implementation of the first energy tagging processes. NERC Tags were first introduced in 1997, in response to the need to track the increasingly complicated energy transactions which were produced as a result of the beginning of electric deregulation in North America.