2026 official-source estimate
Estimate Illinois withholding with the 2026 IL-700-T automated payroll method and Form IL-W-4 allowances.
Quick answer
Illinois: Estimate Illinois withholding with the 2026 IL-700-T automated payroll method and Form IL-W-4 allowances. This 2026 calculator combines that state treatment with federal withholding and FICA, while showing supported employee-paid programs and known exclusions explicitly.
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Included
Limitations
Enter gross pay for one pay period, federal W-4 adjustments, and the state details shown above. Federal withholding follows Publication 15-T. Illinois uses the automated payroll formula in the 2026 IL-700-T: current wages are reduced by the pay-period value of the employee's Form IL-W-4 Line 1 and Line 2 allowances, then the 4.95% withholding rate and any additional amount are applied.
Example: Line 1 and Line 2 allowances have different annual values under IL-700-T, so the calculator asks for them separately rather than combining them. The calculator does not assume any unentered benefit deduction or invent a tax result.
Weekly, biweekly, semimonthly, and monthly are the supported paycheck frequencies. “Annual salary” is an earnings input and the annual view is a simple period multiplication; neither is an annual payroll-period method. The special Form W-4 adjustment for nonresident aliens is not modeled.
State paycheck questions
Federal withholding follows Publication 15-T. Illinois uses the automated payroll formula in the 2026 IL-700-T: current wages are reduced by the pay-period value of the employee's Form IL-W-4 Line 1 and Line 2 allowances, then the 4.95% withholding rate and any additional amount are applied.
Included in this estimate: Federal income tax withholding; Social Security and Medicare; 2026 Illinois 4.95% withholding method; Form IL-W-4 Line 1 and Line 2 allowances.
Not included in this estimate: Unentered employer benefits and unsupported deduction treatments; Reciprocity and nonresident exceptions; Prior-period payroll corrections; Employer-specific payroll settings.
Source trail
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