To find out if you qualify, write a letter of request to the Illinois Department of Revenue, Sales. To form a charitable organization, there are three major governmental bodies that every charitable organization operating in the state of Illinois must contact.Fill out form either: Form 1023. Applicants will need to complete the online application in full, including all requested documents and forms. 501(c)(3) nonprofits apply using Form 1023 or Form 1023-EZ. This guide covers the required filings to maintain a nonprofit corporation in Illinois. Every year you'll need to fill out and submit either IRS Form 990, 990EZ, or 990N, depending on your organization's financial activities. , County of ______: ss. File Form 1023 for federal tax exemption. Apply for Illinois tax exemptions.