(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 or workers' compensation surcharge by the date required by Section 251.002, the rate of assessment is the rate applied in the previous tax or surcharge period.
(b) If the commissioner advises the comptroller of the applicable rate of assessment of a maintenance tax or workers' compensation surcharge after the tax or surcharge has been assessed, the comptroller shall:
(1) advise each taxpayer or surcharge payer in writing of the amount of any additional taxes or surcharges due; or
(2) refund any excess taxes or surcharges paid.