Williamson County Equalization Factor Set at 1.0165

Release Date: 04/21/2026

2025 Williamson County Tentative Multiplier Announced

For Immediate Release Date: 21-Apr-2026
Letter lD: L1222483432
Contact: Maura Kownacki 312.814.1777 SPRINGFIELD, IL, Williamson County has been issued a tentative property assessment equalization factor of 1.0165, according to David Harris, director of the Illinois Department of Revenue (IDOR).
The property assessment equalization factor, often called the "multiplier," is the method used to achieve uniform property assessments among counties, as required by law. This equalization is particularly important because some of the state's 6,600 local taxing districts overlap into two or more counties (e.g., school districts, junior college districts, fire protection districts). If there was no equalization among counties, substantial inequities among taxpayers with comparable properties would result.
State law requires property in Illinois to be assessed at one-third (1/3) of its market value. Farm property is assessed differently with farm homesites and dwellings subject to regular assessing and equalization procedures. Farmland and farm buildings are assessed according to standards based on productivity.
The equalization factor is determined annually for each county by comparing the sales price of individual properties sold over the past three years to the assessed value placed on those properties by the county supervisor of assessments/ county assessor.
If the three-year average level of assessment is one-third of market value, the equalization factor will be one (1.0000). If the average level of assessment is greater than one-third of market value, the equalization factor will be less than one (1.0000). And if the average level of assessment is less than one-third of market value, the equalization factor will be greater than one (1.0000).
Assessments in Williamson County are at 32.79% of market value, based on sales of properties in 2022, 2023, and 2024.
The equalization factor currently being assigned is for taxes, 2025 payable in 2026.
Last year's equalization factor for the county was 1.0874.
The tentative factor is subject to change (1) if the County Board of Review takes actions which significantly affect the county assessments, or (2) if local officials or others can present data showing that IDOR's estimates of the average level of assessments in the county should be adjusted. A public hearing on the tentative multiplier will be held between 20 and 30 days after the tentative factor is published in a newspaper of general circulation within the county.
A change in the equalization factor does not mean total property tax bills will increase or decrease. Tax bills are determined by local taxing bodies when they request money each year to provide services to local citizens. If the amount requested by local taxing districts is not greater than the amount received in the previous year, then total property taxes will not increase even if assessments may have increased.
The assessed value of an individual property determines what portion of the tax burden a specific taxpayer will assume. That individual's portion of tax responsibility is not changed by the multiplier.
- 2025 Williamson County Tentative Multiplier Announced
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