If you believe that the public records are inaccurate, you should contact your local county’s assessment department to request that the data be reviewed. The process varies by location; some may ask you to file an appeal or submit a grievance. It may help to submit the recent appraisal, or property measurements done by a certified appraiser, to the department to review and make any adjustments if necessary.
Square footage will affect your home’s assessed value, but it also has an affect on how much property tax you pay. If the actual measurements result in more square footage than the county tax assessment office has recorded, using the higher square footage calculation could increase the value of your home. That’s great if you want to sell, but it may also increase your property taxes.