220 ILCS 5/8-303
Where, within 30 days of receipt of a utility bill, a customer alleges that the level of consumption reflected in his utility bill is unreasonably high, it shall be the responsibility of the public utility furnishing natural or artificial gas, electricity or water to that customer to investigate the allegation. If as a result of such an investigation, the public utility determines that the customer's line has been tapped, the utility shall attempt to ascertain the identity of the third party benefiting from the usage of the utility service or for payment for all or part of the disputed charges. If the utility determines that the landlord of the building or his agent is the party who benefited from the usage of the utility service, either the utility or the customer may petition the court for the appointment of receiver to collect the rents due and to remit a portion to the utility company for payment of bills for the tapped service, for current bills and for any expenses incurred by the utility as a result of the tap. The receiver shall make all reasonable efforts, including the obtaining of court orders, to provide to the utility access to the building. Any changes in the building's piping which are necessitated by the tap shall be at the expense of the person benefiting from the tap.
If the utility determines that the landlord of the building is not the party who benefited from the usage of the utility service, the customer shall be so notified and shall also be informed by the utility of a right to register a dispute pursuant to procedures developed by the Commission for resolution of disputed bills, including his right to bring a complaint before the Commission if an agreement with the utility cannot be reached.
In order to enable the customer to ascertain whether the level of consumption is greater than the amounts billed in other billing periods and to eliminate to the fullest extent practicable consecutive estimated bills, the public utility shall make an actual meter reading at least every second billing period. If a meter reader is unable to gain access to the meter for the purpose of making an actual reading, the public utility shall take other appropriate and reasonable measures to read the meter.
Nothing in this Section shall preclude either the customer or the public utility from filing a complaint with the State's Attorney located in the county where the utility service is being rendered to allege an unlawful theft of the customer's utility service.
220 ILCS 5/8-303