225 ILCS 85/41

(a) Upon request, a pharmacy must disclose the current usual and customary retail price of any brand or generic prescription drug or medical device that the pharmacy offers for sale to the public. This disclosure requirement applies only to requests made in person or by telephone. Prices quoted are for informational purposes only and are valid only on the day of inquiry. The requests must specify the name, strength and quantity of the prescription drug. (b) A pharmacy must post a notice informing customers that they may request, in person or by telephone, the current usual and customary retail price of any brand or generic prescription drug or medical device that the pharmacy offers for sale to the public.