Use this Unsworn Declaration form if you are not planning to attend a hearing in-person, or are requesting a phone/video hearing. The form must be filled completely and does not require to be notarized.
The appraisal district will also accept the Texas State Comptroller’s, Property Owner’s Affidavit of Evidence (50-283) form but it must be notarized.
You can find the document here: https://comptroller.texas.gov/forms/50-283.pdf