(a) Except as provided by Subsection (b), if the commissioner does not advise the comptroller of the applicable rate of assessment of a maintenance tax by the date required by Section 251.002, the rate of assessment is the rate applied in the previous tax period.
(b) If the commissioner advises the comptroller of the applicable rate of assessment of a maintenance tax after the tax has been assessed, the comptroller shall:
(1) advise each taxpayer in writing of the amount of any additional taxes due; or
(2) refund any excess taxes paid.