If any due date falls on a Saturday,. You must file Form IL-W-4 when Illinois.Income Tax is required to be withheld from compensation that you receive as an em- ployee. The foregoing shall include compliance with all laws, regulations, directives or orders pertaining to civil rights and equal employment opportunity legislation. Government ; Local Government. Our Veterans workstudy program can help you earn money while you're enrolled in a college, vocational school, or professional training program. Download and complete Divorce, Child Support, and Maintenance forms from the Illinois Office of the Courts. Securing your today and tomorrow. Find out how much you'll pay in Illinois state income taxes given your annual income. Customize using your filing status, deductions, exemptions and more.