International Fuel Tax Agreement (IFTA) — a plan involving a majority of the 48 contiguous states, most of which require interstate motor carriers to report how much fuel they use within the borders of their state for taxing purposes. Under IFTA, such carriers may report fuel used in all such states to one base state. Each motor carrier must maintain a complete record of all fuel purchased and used in its operations, together with detailed mileage records on an individual vehicle basis. A state's fuel "use" tax enables it to assess highway user fees on all motor carriers that travel on its roads, not just those that purchase fuel within the state and pay the tax at the fuel pump.