Come December 15, get ready to fish out double the toll tax if FASTag is missing from your vehicle. To prevent congestion at toll plazas, the government has made it mandatory to declare all lanes at toll fee plaza on national highways as FASTag lanes . FASTag is an electronic toll collection system, operated by the NHAI. Based on radio frequency identification (RFID) technology, FASTag is affixed on the windscreen of vehicles. In other words, FASTags are prepaid rechargeable tags for toll collection. FASTags do not have any expiry date, hence, they can be used as long as they are not tampered with and are readable at the toll plazas.