The underestimation penalty shall apply to those public utilities subject to paragraph (1) of subsection (d) and shall be calculated after the filing of the amended return. It shall be imposed if the amount actually paid on any of the dates specified in subsection (f) is not equal to at least one-fourth of the amount actually due for the year, and shall equal the greater of:
If the amount determined as provided in item (3) of this subsection exceeds 50% of the previous fiscal year's appropriation level, the Commission shall then compute the proportionate amount, if any, which (x) the tax paid hereunder by each utility during the preceding biennium, and (y) the amount paid into the Public Utility Fund during the preceding biennium by the Department of Revenue pursuant to Sections 2-9 and 2-11 of the Electricity Excise Tax Law, bears to the difference between the amount determined as provided in item (3) of this subsection (i) and 50% of the previous fiscal year's appropriation level. The Commission shall cause the proportionate amount determined with respect to payments made under the Electricity Excise Tax Law to be transferred into the General Revenue Fund in the State Treasury, and notify each public utility that it may file during the 3 month period after the date of notification a claim for credit for the proportionate amount determined with respect to payments made hereunder by the public utility. If the proportionate amount is less than $10, no notification will be sent by the Commission, and no right to a claim exists as to that amount. Upon the filing of a claim for credit within the period provided, the Commission shall issue a credit memorandum in such amount to such public utility. Any claim for credit filed after the period provided for in this Section is void.
If the amount determined as provided in paragraph (3) of this subsection (i-5) results in a deficit, the Commission may assess electric utilities and gas utilities for the difference between the amount appropriated for the ordinary and contingent expenses of the Commission and the amount derived under paragraph (1) of this subsection (i-5). Such proceeds shall be deposited in the Public Utility Fund in the State treasury. The Commission shall apportion that difference among those public utilities on the basis of each utility's share of the total intrastate gross revenues of the utilities subject to this subsection (i-5). Payments required under this subsection (i-5) shall be made in the time and manner directed by the Commission. The Commission shall permit utilities to recover Illinois Commerce Commission assessments effective pursuant to this subsection through an automatic adjustment mechanism that is incorporated into an existing tariff that recovers costs associated with this Section, or through a supplemental customer charge.
Within 6 months after the first time assessments are made under this subsection (i-5), the Commission shall initiate a docketed proceeding in which it shall consider, in addition to assessments from electric and gas utilities subject to this subsection, the raising of assessments from, or the payment of fees by, water and sewer utilities, entities possessing certificates of service authority as alternative retail electric suppliers under Section 16-115 of this Act, entities possessing certificates of service authority as alternative gas suppliers under Section 19-110 of this Act, and telecommunications carriers providing local exchange telecommunications service or interexchange telecommunications service under Sections 13-204 or 13-205 of this Act. The amounts so determined shall be based on the costs to the agency of the exercise of its regulatory and supervisory functions with regard to the different industries and service providers subject to the proceeding. No less often than every 3 years after the end of a proceeding under this subsection (i-5), the Commission shall initiate another proceeding for that purpose.
The Commission may use this apportionment method until the docketed proceeding in which the Commission considers the raising of assessments from other entities subject to its jurisdiction under this Act has concluded. No credit memoranda shall be issued pursuant to subsection (i) if the amount determined as provided in paragraph (3) of this subsection (i-5) results in a deficit.
220 ILCS 5/2-202