If your employer in any of these states withheld that state's tax from your compensation, you may file the correct form with that state to claim a refund. Use the following pages to complete your Illinois State and Federal income tax withholding, or W-4 information.The Attorney General's Disability Rights Bureau enforces state and federal laws that protect the rights of people with disabilities in Illinois. Request to withhold taxes. Submit a request to pay taxes on your Social Security benefit throughout the year instead of paying a large bill at tax time. To apply: Cook County Assessor's Office. Gov website belongs to an official government organization in the United States. Please complete a paper or electronic PDF Form W-4 to modify state tax withholding. Reference the table below to see a list of state tax forms. The general deadline for federal and Illinois state 2024 tax filings is Tuesday, April 15, 2025.