FASTag is basically Radio Frequency Identification (RFID) technology passive tag. This tag has been designed so that the vehicle owners are able to make the toll payments directly from their account while the vehicle is in motion. So, in short the vehicle does not have to stop to make any kind of payment. This tag has been made compulsory by Ministry of Road Transport and Highways for all the vehicles (private and commercial) with effect from 1st December 2019.  This tag will be put on the windscreen of every vehicle