In the Gas Distribution business Unaccounted Gas is referred to by various names or terms such as: Lost and Unaccounted-For, LUG, L&U, and UAF. In simplest terms, Unaccounted Gas is the result of the formula “gas receipts minus gas deliveries”. For the Measurement Group the process amounts to a “gas inventory reconciliation” based on the recorded volumes into the system(s) less the sum of the volumes out of the system(s). This can be a town by town or a total-system reconciliation. In a perfect world the gas receipt point is a single town border or city gate, and the deliveries are made to customers via a totally gas tight piping system. The city gate station measurement period and that of the customers’ meters are all based on the same time period. All meters have an uncertainty of less than 0.5%. All of the volume determinations and reporting is done in a single Gas Measurement System, and no revisions to “original” volumes is ever necessary. Regrettably not too many perfect world situations exist in the gas distribution business