Texas Tax Code - TAX § 33.44. Joinder of Other Taxing Units

(a) A taxing unit filing suit to foreclose a tax lien on real property shall join other taxing units that have claims for delinquent taxes against all or part of the same property.

(b) For purposes of joining a county, citation may be served on the county tax assessor-collector.  For purposes of joining any other taxing unit, citation may be served on the officer charged with collecting taxes for the unit or on the presiding officer or secretary of the governing body of the unit.  Citation may be served by certified mail, return receipt requested.  A person on whom service is authorized by this subsection may waive the issuance and service of citation in behalf of his taxing unit.

(c) A taxing unit joined in a suit as provided by this section must file its claim for delinquent taxes against the property or its lien on the property is extinguished.  The court's judgment in the suit shall reflect the extinguishment of a lien under this subsection.