Tax Code §5.16

(a) The comptroller may inspect the records or other materials of an appraisal office or taxing unit, including the relevant records and materials in the possession or control of a consultant, advisor, or expert hired by the appraisal office or taxing unit, for the purpose of: (1) establishing, reviewing, or evaluating the value of or an appraisal of any property; or (2) conducting a study, review, or audit required by Section 5.10 or 5.102 or by Section 403.302 , Government Code. (b) On request of the comptroller, the chief appraiser or administrative head of the taxing unit shall produce the materials in the form and manner prescribed by the comptroller.