Texas Local Government Code - LOC GOV'T § 375.117. Area to be Assessed

(a) The area of the district to be assessed according to the findings of the board may be the entire district or any part of the district and may be less than the area proposed in the notice of the hearing.

(b) Except as provided by Subsection (c), the area to be assessed may not include property that is not within the district boundaries at the time of the hearing unless there is an additional hearing, preceded by the required notice.

(c) The owner of improvements constructed or land annexed to the district after the district has imposed assessments may waive the right to notice and an assessment hearing and may agree to the imposition and payment of assessments at an agreed rate for improvements constructed or land annexed to the district.