I don't disclose the actual square footage to the assessor but I might comment to them that their square footage is reported as 1,800 square feet but the garage has not been enclosed into livable area and the actual heated/cooled, finished livable area is less than the 1,800 square feet. The assessor's office gets a permit for a garage enclosure for example, drive by, see an exterior wall instead of a garage door and add that area to the livable area. But they don't see the interior and maybe all the property owner did was take the door down and put up some exterior siding without every doing anything to the interior. If that property is one I am completing an appraisal report on, I report what I have seen and what the property taxes are based on in the appraisal report. I will also tell the property owner to go check out the information in the assessor's office because it appears that they are being taxed on too much livable area. Some times I will get back to the assessor's office and sometimes I won't, but the property owner does get a notice from me that they do need to check into their assessment. But I do not disclose any additional livable area to the assessor as that would raise their taxes (although I am muttering to myself as a tax payer, I am having to pay that person's taxes because the assessment records are not correct). The assessor's offices here are full time, open from 8AM to 5PM and are the main source of info for any property in the county (gossip too, which they have to know to keep the ownership records straight). Since the majority of sales are for sale by owner, they usually know who is related to who, why the person sold, why the person bought, who is the second cousin or neighbor or person to contact that would know about the sale terms and condition of the property, etc, etc, etc. Since they can provide me with so much valuable information, I try to provide what I can without violating any confidentiality. Besides if someone sees my car parked in front of a house, the entire county knows five minutes after I ring the doorbell, who is refinancing or selling! There aren't any secrets in a small town!!