A party may direct written interrogatories to any other party. A copy of the interrogatories shall be served on all other parties entitled to notice.Interrogatories are written questions that one party sends to the other. The receiving party is required to answer these questions under oath. It can be tricky to navigate the vast Cook County court system. The Chicago litigation attorneys at Smoler Law can help. A party may serve on any other party no more than 25 written interrogatories, including all discrete subparts. It provided for discovery of documents and tangible things, and for entry upon real estate, in the custody or control of any party or other person. Download the form: Get the list of interrogatories. If personally served, responses to interrogatories are due within thirty (30) days of service.