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How to Calculate 2020 Illinois State Income Tax by Using State Income Tax Table

1. Find your income exemptions

2. Find your pretax deductions, including 401K, flexible account contributions ...

3. Find your gross income

4. Check the 2020 Illinois state tax rate and the rules to calculate state income tax

5. Calculate your state income tax step by step

6. If you want to simplify payroll tax calculations, you can download ezPaycheck payroll software, which can calculate federal tax, state tax, Medicare tax, Social Security Tax and other taxes for you automatically. You can try it free for 30 days, with no obligation and no credt card needed.

Learn more about the in house payroll tax solution for Illinois small businesses here.
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ezPaycheck: Small Business Payroll Solution

Illinois State Tax Tables

Tax rate used in calculating Illinois state tax for year 2020

State Abbreviation:


State Tax Withholding State Code:


Acceptable Exemption Form:


Basis For Withholding:

State Exemptions

Acceptable Exemption Data:

0 / Number of Regular Allowances / Number of Additional Exemptions

TSP Deferred:


Special Coding:

Determine the Total Number Of Allowances field as follows:
First Position - Enter 0 (zero).
Second and Third Positions - Enter the number of exemptions claimed.

Determine the Additional Exemptions Claimed field as follows:
First and Second Positions - Enter the number of additional allowances claimed on Line 2 of the IL-W-4. Valid values are 00 through 99. If no allowances are claimed, enter 00.

Additional Information:


Withholding Formula (Illinois Effective 2020)
  1. Subtract the biweekly Thrift Savings Plan contribution from the gross biweekly wages.

  2. Multiply the adjusted gross biweekly wages times 26 to obtain the annual wages.

  3. Determine the exemption allowance by applying the following guideline and subtract this amount from the annual wages.

    Exemption Allowance = $2,275 x Number of Exemptions

  4. Determine the additional allowance by applying the following guideline and subtract this amount from step 3 to compute the taxable income.

    Additional Allowance = $1,000 x Number of Additional Exemptions

  5. Multiply the taxable income computed in step 4 times 4.95 percent to determine the amount of Illinois tax withholding.

  6. Divide the annual Illinois tax withholding by 26 to obtain the biweekly Illinois tax withholding.

More Payroll Information for Illinois Small Business

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  • Quick Start Guide for New Payroll Software Customers

  • How to start payroll in mid-year

  • How to handle tips in restaurants

  • How to handle the local taxes

  • How to print paycheck on blank stock

  • How to add a customized deduction and withhold it automatically

  • How to set up payroll tax options for church and non-profits

  • How to handle paychecks for both employees and contractors

  • How to file tax forms

  • How to enter the paychecks for after the fact payroll