Things You'll Need

Instructions

Calculate Your Illinois State Income Tax

1

Watch for your W-2 earnings statement to arrive from your employer as tax season approaches. This statement will contain a summary of your yearly wage earnings, detailing any federal and state taxes that have been withheld from your salary. Business owners and self-employed individuals do not receive W-2 forms and are required to report income independently.
2

Remember to include all income sources, not just what you earned at your job. You will have to pay taxes on any cash profits realized through investments, though exceptions apply in cases where you still hold the investment instead of selling it for its cash value. If you've been remembered in someone's will, won money in the lottery, received a cash award, or accepted non-repayable student funding, you will have to include such amounts as part of your total income.
3

Total the value of the income tax deductions for which you qualify. It may benefit you to work with a tax preparation professional if you have difficulties with tax deductions, since the fees you pay to have your taxes professionally prepared may pay for themselves when you save on your income taxes.
4

Calculate your Illinois state income tax using the state's flat rate. Take your taxable income, which is your total income minus any tax deductions, and multiply it by the flat rate to learn the amount of money you'll be paying in state income tax.
5

File your tax return by the April 15 deadline or whatever deadline is being used if April 15 falls on a day when mail service is not in operation. You can also take advantage of online services to submit your tax return electronically.