A LOMC is a letter which reflects an official change to an effective FIRM.

LOMCs are issued in response to a request for FEMA to amend or revise its effective flood map to remove a property or reflect changed flooding conditions on the effective map.

When certain technical or scientific evidence is available that proves that a property has been inadvertently mapped in a Special Flood Hazard Area (SFHA), or flood hazard data needs to be revised due to man-made changes, a request to FEMA for a LOMC may be submitted.