Tex. Tax Code § 26.15

(a) Except as provided by Chapters 41 and 42 of this code and in this section, the tax roll for a taxing unit may not be changed after it is completed.

(b) The assessor for a unit shall enter on the tax roll the changes made in the appraisal roll as provided by Section 25.25 of this code.

(c) At any time, the governing body of a taxing unit, on motion of the assessor for the unit or of a property owner, shall direct by written order changes in the tax roll to correct errors in the mathematical computation of a tax. The assessor shall enter the corrections ordered by the governing body.

(d) Except as provided by Subsection (e) of this section, if a correction in the tax roll that changes the tax liability of a property owner is made after the tax bill is mailed, the assessor shall prepare and mail a corrected tax bill in the manner provided by Chapter 31 of this code for tax bills generally. He shall include with the bill a brief explanation of the reason for and effect of the corrected bill.

(e) If a correction that increases the tax liability of a property owner is made after the tax is paid, the assessor shall prepare and mail a supplemental tax bill in the manner provided by Chapter 31 of this code for tax bills generally. He shall include with the supplemental bill a brief explanation of the reason for and effect of the supplemental bill. The additional tax is due on receipt of the supplemental bill and becomes delinquent if not paid before the delinquency date prescribed by Chapter 31 of this code or before the first day of the next month after the date of the mailing that will provide at least 21 days for payment of the tax, whichever is later.

(f) If a correction that decreases the tax liability of a property owner is made after the owner has paid the tax, the taxing unit shall refund to the property owner who paid the tax the difference between the tax paid and the tax legally due, except as provided by Section 25.25(n). A property owner is not required to apply for a refund under this subsection to receive the refund.

(g) A taxing unit that determines a taxpayer is delinquent in ad valorem tax payments on property other than the property for which liability for a refund arises or for a tax year other than the tax year for which liability for a refund arises may apply the amount of an overpayment to the payment of the delinquent taxes if the taxpayer was the sole owner of the property:

(1) for which the refund is sought on January 1 of the tax year in which the taxes that were overpaid were assessed; and

(2) on which the taxes are delinquent on January 1 of the tax year for which the delinquent taxes were assessed.

(h) The assessor for a school district shall correct the tax roll for the district for the 2025 tax year to reflect the results of the election to approve the constitutional amendment proposed by S.J.R. 2, 89th Legislature, Regular Session, 2025. This subsection expires December 31, 2026.

(h) The assessor for a school district shall correct the tax roll for the district for the 2025 tax year to reflect the results of the election to approve the constitutional amendment proposed by S.J.R. 85, 89th Legislature, Regular Session, 2025. This subsection expires December 31, 2026.