Illinois Checklist is an online tool that helps individuals and businesses in the state of Illinois stay up-to-date on their tax filing requirements and other important information. The Checklist provides step-by-step guides and checklists to help users file their taxes correctly, as well as information and links to other resources to help them understand their tax obligations. It also provides access to helpful tools and calculators to help taxpayers estimate their tax liability and make informed decisions. There are four types of Illinois Checklist: 1. Individual Income Tax Checklist 2. Business Income Tax Checklist 3. Sales Tax Checklist 4. Property Tax Checklist.