Illinois Statutes Chapter 70. Special Districts § 3705/7.4. Billing for services

(1) shall bill for any utility service, including previously unbilled service: (A) within 12 months after the provision of that service to the customer if the service is supplied to a residential customer; or (B) within 24 months after the provision of that service to that customer if the service is supplied to a non-residential customer; however, the public water district may bill for unpaid amounts that were billed to a customer or if the customer was notified that there is an unpaid amount before the effective date of this amendatory Act of the 100th General Assembly for service that was supplied to the customer before January 1, 2016;

(2) shall not intentionally delay billing beyond the normal billing cycle;

(3) shall label any amount attributed to previously unbilled service as such on the customer's bill and include the beginning and ending dates for the period during which the previously unbilled amount accrued;

(4) shall issue the makeup billing amount calculated on a prorated basis to reflect the varying rates for previously unbilled service accrued over a period of time when the rates for service have varied; and

(5) shall provide the customer with the option of a payment arrangement to retire the makeup bill for previously unbilled service by periodic payments, without interest or late fees, over a time equal to the amount of time the billing was delayed.