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Illinois Income Tax Forms

Illinois Income Tax Forms

Individual Income Tax

Form IL-1040 Individual Income Tax Retur

Form IL-1040-X Amended Individual Income Tax Return

Corporate Income Tax 

Form IL-1120 Corporation Income and Replacement Tax Return 

Form IL-1120-X Amended Corporation Income and Replacement Tax Return

Illinois Income Tax Forms: A Complete Guide

Income tax forms are the most dreaded part of tax season. With new rules and regulations, unlimited categories, and applicable rates, it is no wonder why many individuals wait until the last minute to file their taxes. However, tax season can be a lot less stressful if you have a clear understanding of the forms you need to file and the process you need to follow. In this article, we will discuss Illinois income tax forms, what forms you would need to file, and how you could file them.

What is Illinois Income Tax?

In the state of Illinois, the government requires that all residents’ report their incomes and pay taxes on both federal and state levels. Illinois income tax is a tax that residents of Illinois pay on their income. The Illinois state government uses the income tax to pay for public services such as education, health, social welfare, and infrastructure projects.

The Illinois Department of Revenue administers the tax collection.

Illinois Income Tax Rates

The income tax rate for Illinois residents is a flat 4.95% of their net income. So, any person who earns an income in Illinois pays 4.95% of their net income to the state government. This rate applies to individuals, partnerships, corporations, and trusts. Employees of corporations have their Illinois income tax deducted from their paychecks by their employer(s).

Illinois Income Tax Forms

The Illinois income tax forms you need to complete are based on your tax situation. A tax situation is individual and depends on your source(s) of income. Below is an overview of the Illinois income tax forms you may need to complete and file:

Form IL-1040 Individual Income Tax Return

Form IL-1040 is the most common income tax return form used by resident individuals filing their personal income tax returns in Illinois. This form is used to report all sources of income, tax credit claims, and tax exemptions. Resident persons could file the form electronically by using MyTax Illinois website or mail it to the Illinois Department of Revenue.

Form IL-1040-ES, Estimated Income Tax Payments for Individuals

Form IL-1040-ES is for individuals who are self-employed or have income that requires that they must pay estimated taxes throughout the year. This form is used to calculate the first three estimated tax payments for the current tax year. Form IL-1040-ES could be completed electronically or manually and mailed to the Illinois Department of Revenue.

Form IL-1040-X, Amended Individual Income Tax Return

Form IL-1040-X is the form to use if an individual needs to make any changes or errors in their original income tax return. The changes could be related to wages, rental properties, or any other matter affecting the return. This form must be submitted within three years after the original tax due date.

Form IL-505-I, Automatic Extension Payment

Form IL-505-I allows individuals to request an automatic six-month extension of time to file the individual quarterly estimated income tax payments. Provided its requirement is met, the automatic extension will extend the time to file, but not to make, the tax payments to the Illinois Department of Revenue.

Form IL-2848, Power of Attorney and Declaration of Representative

Form IL-2848 is a tax form that allows individuals to permit someone else, usually, an attorney, to handle their tax matters. This form authorizes the person to receive the tax documents and information relating to the tax return or tax documents. This form must be submitted to the Illinois Department of Revenue.

Form IL-W-4, Employee’s Illinois Withholding Allowance Certificate

Form IL-W-4 is a form used by employees in Illinois. This form provides their employer with information about how much income tax should be withheld from the employee’s paychecks.

Form IL-1040 Schedule M – Other Additions and Subtractions for the Full-Year

Form IL-1040 Schedule M is for Illinois full-year residents who need to claim an income modification. The modifications are either subtraction or addition when calculating their income tax liability. This form must include all supporting documents and should be filed with Form IL-1040.

Illinois Income Tax Due Dates and Penalties

The due date to file and pay individual income tax returns in Illinois is generally April 15, but this date could vary. If this date falls on a weekend, the tax due date is the following Monday. For individuals on extension, the tax is due on October 15, provided that the previous year is filed. Late payment or non-payment of income tax may result in several penalties, including additional interest, filing fees, and even criminal prosecution.


Income tax forms can be daunting, especially if you are filing for the first time. However, there are Illinois government resources available to alleviate the pressure of filing taxes. To start, have all the necessary documents ready and approach the process with a clear and open mindset. Knowing which Illinois income tax form(s) to file significantly improves your filing process. Filing taxes before the deadline reduces the chances of missing out on tax returns or incurring fines and penalties. Follow the steps outlined in the Illinois tax forms discussed in this article to complete your individual income taxes for Illinois. And remember, if you are struggling with the process, consult with a tax professional.