Generally, only a nonresident alien individual may use the terms of a tax treaty to reduce or eliminate U.S. tax on certain types of income. Use this tool to estimate the federal income tax you want your employer to withhold from your paycheck.This is tax withholding. Not all forms are listed. 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. Download a copy of your 1099 or 1042S tax form so you can report your Social Security income on your tax return. Fill out an application, compare plans, and enroll in health coverage for 2025. Open Enrollment ends January 15. Semi-weekly payments are due three to seven days after every payroll.