TAXES 19-15, Illinois State Income Tax Withholding

Published: February 25, 2019
Effective: Pay Period 03, 2019


The State of Illinois annual exemption amount for the basic allowances claimed for taxpayer, spouse, and other dependents will increase from $2,225 to $2,275.

No action on the part of the employee or the personnel office is necessary.

Tax Formula

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 or 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.

Withholding Formula (Effective Pay Period 03, 2019)

  1. Subtract the nontaxable biweekly Thrift Savings Plan (TSP) contribution from the gross biweekly wages.
  2. Subtract the nontaxable biweekly Federal Health Benefits Plan payment(s) (includes dental and vision insurance program and Flexible Spending Account - health care and dependent care deductions) from the amount computed in step 1.
  3. Add the taxable biweekly fringe benefits (e.g., taxable life insurance) to the amount computed in step 2 to obtain the adjusted gross biweekly wages.
  4. Multiply the adjusted gross biweekly wages by the number of pay dates in the tax year to obtain the annual wages.
  5. 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

  6. Determine the additional allowance by applying the following guideline, and subtract this amount from step 5 to compute the taxable income:

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

  7. Multiply annualized taxable wages by 4.95 percent to determine the annual tax.
  8. Divide the annual Illinois tax withholding calculated in step 7 by the number of pay dates in the tax year to obtain the biweekly Illinois tax withholding.


To view the updated tax formula, go to the HR and Payroll Clients page from the MyNFC drop-down menu on the National Finance Center (NFC) homepage. Select the Publications tab and select U.S. Income Tax Formulas from the Publications menu to launch the tax map. Select the desired State from the map provided for the formula.


For questions about NFC processing, authorized Servicing Personnel Office representatives should contact the NFC Contact Center at 1-855-NFC-4GOV (1-855-632-4468) or via the customer service portal.