Tex. Tax Code § 23.013

(a) If the chief appraiser uses the market data comparison method of appraisal to determine the market value of real property, the chief appraiser shall use comparable sales data and shall adjust the comparable sales to the subject property.

(b) A sale is not considered to be a comparable sale unless the sale occurred within 24 months of the date as of which the market value of the subject property is to be determined, except that a sale that did not occur during that period may be considered to be a comparable sale if enough comparable properties were not sold during that period to constitute a representative sample.

(b-1) Notwithstanding Subsection (b), for a residential property in a county with a population of more than 150,000, a sale is not considered to be a comparable sale unless the sale occurred within 36 months of the date as of which the market value of the subject property is to be determined, regardless of the number of comparable properties sold during that period.

(c) A sale of a comparable property must be appropriately adjusted for any change in the market value of the comparable property during the period between the date of the sale of the comparable property and the date as of which the market value of the subject property is to be determined.

(d) Whether a property is comparable to the subject property shall be determined based on similarities with regard to location, square footage of the lot and improvements, property age, property condition, property access, amenities, views, income, operating expenses, occupancy, and the existence of easements, deed restrictions, or other legal burdens affecting marketability.

(e) In this subsection, "designated historic district" means an area that is zoned or otherwise designated as a historic district under municipal, state, or federal law. In determining the market value of residential real property located in a designated historic district, the chief appraiser shall consider the effect on the property's value of any restriction placed by the historic district on the property owner's ability to alter, improve, or repair the property.

(f) Notwithstanding Section 1.04(7)(C), in determining the market value of real property, a chief appraiser may not consider the price paid by this state or the United States to purchase a parcel of or an easement in real property described by Section 11.38(a) if the purchase was for the purpose of installing or constructing on the property border security infrastructure as defined by Section 11.38(b)(1).