Illinois Income Tax Withholding Payment and Filing Requirements
Employers in Illinois must conform with these state rules relating to filing income tax withholding returns.
Periodic Returns. Quarterly (Form IL-941) due by last day of the month following the quarter. Annually (Form IL-941) due by January 31 of the following year. Semi-weekly payments, or monthly (Form 501 with payment by the 15th day of the following month) payments, may be required of some employers.
Annual Reconciliation Returns. None (Form IL-W-3 no longer required)