Tex. R. Civ. P. 241

As amended through August 27, 2021
Rule 241 - Assessing Damages on Liquidated Demands

When a judgment by default is rendered against the defendant, or all of several defendants, if the claim is liquidated and proved by an instrument in writing, the damages shall be assessed by the court, or under its direction, and final judgment shall be rendered therefor, unless the defendant shall demand and be entitled to a trial by jury.

Tex. R. Civ. P. 241