Texas Tax Code - TAX § 171.1532. Business on Which Tax on Net Taxable Margin Is Based

(a) The tax covering the privilege periods included on the initial report is based on the business done by the taxable entity during the period beginning on the taxable entity's beginning date and:

(b) The tax covering the regular annual period, other than a regular annual period included on the initial report, is based on the business done by the taxable entity during the period beginning with the day after the last date upon which taxable margin or net taxable earned surplus on a previous report was based and ending with its last accounting period ending date for federal income tax purposes in the year before the year in which the report is originally due.