Tex. Gov't Code § 403.214

The state may bring a counterclaim in a suit for a temporary or permanent injunction brought under this subchapter if the counterclaim relates to taxes or fees imposed under the same statute and during the same period as the taxes or fees that are the subject of the suit and if the counterclaim is filed not later than the 30th day before the date set for trial on the merits of the application for a temporary or permanent injunction. The state is not required to make an assessment of the taxes or fees subject to the counterclaim under any other statute, and the period of limitation applicable to an assessment of the taxes or fees does not apply to a counterclaim brought under this section.