You must register with us to withhold Illinois Income Tax.
As a withholding agent (person who withholds income tax), you are liable for the taxes that you are required to withhold. Because we are required to collect taxes (and issue assessments when these taxes are not paid), Illinois law states that the amounts required to be withheld and paid to us (and any penalties and interest) are considered to be a tax on you. As the withholding agent you must pay the tax even if you failed to withhold the tax from your employee.
For more detailed information, see Publication 130, Who is Required to Withhold Illinois Income Tax.
For the current income tax rate, see Income Tax Rates. For more detailed information and the Illinois withholding tax amounts, see
All withholding income tax credits are reported on the Schedule WC. The Schedule WC-I, Withholding Income Tax Credits Information, provides detailed information about the withholding income tax credits, how to calculate them and where to report them.
Illinois withholding income tax payments are made on Form IL-501, Withholding Payment Coupon, and Illinois withholding is reported on Form IL-941, Illinois Withholding Income Tax Return.
IMPORTANT: Make sure to use the correct version of Form IL-941 for the liability period you are filing. This is a calendar year form and each year has its own form. For example, you must use a 2020 Form IL-941 for each quarter in 2020. Also, the Form IL-941 that is available on our website must have the correct federal employer identification number (FEIN) and reporting period so the scanline that is automatically produced will have the correct information. Form IL-941s are processed according to the tax year and the scanline on the form. The scanline is the numeric code number entered on the bottom of the form that includes pertinent information for the taxpayer and filing period. Common error: a Form IL-941 is printed from our website, photocopied, the original data is covered or whited out, and new information is entered. When we receive the Form, it is applied to the period and FEIN represented in the scanline on the bottom of the page. If the scanline is incorrect or cannot be read, then the Form will not be applied to the correct period or taxpayer.