(a) The rate of assessment set by the commissioner may not exceed 0.4 percent of the gross premiums subject to taxation under Section 253.003.
(b) The commissioner shall annually adjust the rate of assessment of the maintenance tax so that the tax imposed that year, together with any unexpended funds produced by the tax, produces the amount the commissioner determines is necessary to pay the expenses during the succeeding year of regulating all classes of insurance specified under Section 253.003.