Flood Insurance Rate Map Interagency Technology Act of 2021 or the FIRM IT Act of 2021 This bill modifies technical requirements for National Flood Insurance Program (NFIP) rate maps (community maps delineating flood hazard areas, flood elevations, and flood risk zones that are applicable to flood insurance rate determination). Specifically, the Federal Emergency Management Agency (FEMA) must consult with the Department of Defense, the U.S. Geological Survey, and the National Oceanic and Atmospheric Administration to obtain information relevant to NFIP rate maps. FEMA may include this data, as well as specified property survey information, in NFIP rate maps. The format of NFIP rate maps must conform to specified data and protocols.