220 ILCS 5/5-106
Each public utility shall have an office in one of the cities, villages or incorporated towns in this State in which its property or some part thereof is located, and shall keep in said office all such books, accounts, papers, records and memoranda as shall be ordered by the Commission to be kept within the State. The address of such office shall be filed with the Commission. No books, accounts, papers, records or memoranda ordered by the Commission to be kept within the State shall be at any time removed from the State, except upon such conditions as may be prescribed by the Commission.
Each public utility shall be liable for, and upon proper invoice from the Commission shall promptly reimburse the Commission for, the reasonable costs and expenses associated with the audit or inspection of any books, accounts, papers, records and memoranda kept outside the State.
In the case of a public utility that provides drinking water services, upon the request of a municipal wastewater agency or unit of local government organized under the Sanitary District Act of 1907, the North Shore Water Reclamation District Act, the Sanitary District Act of 1917, the Metropolitan Water Reclamation District Act, the Sanitary District Act of 1936, the Metro-East Sanitary District Act of 1974, or the Eastern Will Sanitary District Act, such public utility shall provide timely and accurate water usage data, in a format identifiable to the requester, for purposes of calculating wastewater billings. The public utility shall be entitled to collect its reasonable costs incurred to provide such data.
220 ILCS 5/5-106