Texas Tax Code - TAX § 111.008. Deficiency Determination

(a) If the comptroller is not satisfied with a tax report or the amount of the tax required to be paid to the state by a person, the comptroller may compute and determine the amount of tax to be paid from information contained in the report or from any other information available to the comptroller.

(b) On making a determination under this section, the comptroller shall notify the person against whom a determination is made of the determination.  The notice may be given by mail or by personal service.

(c) If the notice is given by mail, it shall be addressed to the taxpayer or other person at the taxpayer's address as it appears in the records of the comptroller.  Service by mail is complete when the notice is deposited in a U.S. Post Office.