220 ILCS 30/10.9
An electric supplier, after notification by the Commission, may file during the 3 month period after the date of notification a claim for credit in such proportionate amount as computed pursuant to Section 2-202 of The Public Utilities Act. 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 electric supplier. Notification of any claim for credit issued prior to October 1, 1975 may be filed within the 3 month period from that date, notwithstanding the preceding sentence. Any claim for credit filed after the period provided for in this Section is void. Credit memoranda issued pursuant to Section 10.6 and this Section may be applied for the 2 year period from the date of issuance against the payment of any amount due during that period under the tax imposed by Section 10.3, or, subject to reasonable rule of the Commission including requirement of notification, may be assigned to any other electric supplier subject to regulation under this Act. Credit memoranda issued prior to October 1, 1975 may be applied for the 2 year period from said date, notwithstanding the preceding sentence. Any application of credit memoranda after the period provided for in this Section is void.
220 ILCS 30/10.9