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Tax Changes Implemented Pay Period (PP) 2023-18 IL


DATE: August 24, 2023
TO: Federal Personnel and Payroll System User Group Representatives
FROM: Christine Zertuche-Rocha, Chief, Payroll Operations Division
SUBJECT: Tax Changes Implemented Pay Period (PP) 2023-18 IL

Please share this information with all impacted employees. The following tax changes were implemented in PP 2023-18. As a result, employees may see a change in their tax withholdings. As a reminder, tax changes are not retroactive to employees’ withholding.

State Tax

Illinois Income Tax Withholding:

  • The state income tax withholding formula has changed effective July 1, 2023.
  • The annual exemption amount for the basic allowances claimed for taxpayers, spouses, and other dependents has changed from $2,625 to $2,225.
  • Datamart Query: Tax State = 17

You may execute Datamart queries to identify employees in affected state taxing areas. For Combined File Ad-Hoc query/analysis of applicable States: add STE Tax State 1 = (State Code above) or STE Tax State 2 = (State Code above) to the filter or prompt lines.

The Interior Business Center (IBC) Payroll website is updated frequently; you may view the state tax formulas here:  Federal, State and Territorial Income Tax Withholding Formulas.

If there are any questions, please call the IBC Customer Support Center at 1-866-367-1272 or by email at