Ill. Admin. Code tit. 83, § 450.140 – Maintenance of Books and Records and Commission Access

a) An electric utility shall maintain books, accounts, and records separate from those of its affiliated interests.
b) In connection with an application for a certificate of service authority filed by an affiliated interest of an electric utility, pursuant to Section 16-115 of the Act, the affiliated interest shall provide a copy of a Commission approved services and facilities or affiliated interest agreement that explicitly sets forth both the cost allocation guidelines and the accounting conventions to be applied to any transactions: between the electric utility and its affiliated interests in competition with ARES; between the utility and its other affiliated interests; and between the utility's affiliated interests in competition with ARES and its other affiliated interests. In the event that there is no Commission approved agreement addressing cost allocation and accounting conventions, the applicant shall submit such an agreement for approval as part of its application.
c) Upon the request of the Commission, electric utilities shall make personnel available who are competent to respond to the Commission's inquiries regarding the nature of any transactions that have taken place between the electric utility and its affiliated interests, including but not limited to the goods and services provided, the prices, terms and conditions, and other considerations given for the goods and services provided.
d) Each electric utility shall maintain a log detailing: each instance in which it exercised discretion in the application of tariff provisions; each instance in which it offered affiliated interests or customers of affiliated interests services not governed by tariffs, except for corporate support transactions and services that have been declared competitive pursuant to Section 16-113 of the Act; and each instance in which it offered affiliated interests or customers of affiliated interests a discount, rebate, fee waiver or waivers of the electric utility's ordinary terms and conditions in connection with services provided under tariffs on file with the Commission. The electric utility shall make such log available to the Commission upon request. The log shall contain the following information:
1. 1) the names of the affiliated interests and unaffiliated entities involved in the transaction;
2. 2) a description of the transaction;
3. 3) the time period over which the transaction applies; and
4. 4) the quantities and locations involved in the transaction.