MLS Sq Footage vs Appraised vs Tax records??

[Erkan Gungor]

bought a house with 1800 sq feet 4br 2 bath on MLS and tax records. The garage is enclosed and basically a bedroom, there is HVAC lighting closet , separate door etc, but no window. I want to install a window and have this room permitted as a 5th bedroom. They already count this room in my square footage.

Does anyone know if getting this permitted will allow me to change the listing to a 5br house? Also can they call out other parts of the house for not being to code while they review my addition? Also how is the sq footage determined?, is that done by the latest appraisal, or is that just owner supplied information that always needs to be verified?

thanks so much, these forums have been amazing.