Why Property Is Reassessed What drives the assessment process? Don't be confused

Each Year by the term quadrennial year. All this means is that real
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property has to be reassessed by law a minimum of every
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four years. The real property assessment can change

each year do to reassessment or a township multiplier

applied at the county level. Even in a quadrennial year if

enough reassessment is not done at the township level by

the assessor the county will apply a county township

multiplier. This process is driven by the Illinois

Department of Revenueís (DOR) Sales Ratio Study.

The study is based on a three year average of three sets

of years sale data for a given township. It is done this

way so that anyone year will not skew the results of the

study in a particular direction. The study done each year

monitors the level of assessment of all good sales (reflects

market value) of real property. The previous year's

assessment is divided by the current yearís sale price.

Ideally it should be 33 1/3% (.3333) the state mandated

level. If the majority of the sales in the study indicate a

level of assessment that is below 33 1/3 percent the

Illinois Department of Revenue computes a tentative

factor to drive assessed values upward in a jurisdiction or

township. The converse is true if the study indicates a

level of assessment above 33 1/3%. Each year as the new

year of sales enter the study and the oldest year of sales

drops out of the study the results are modified by this

exchange of data.

If the assessor makes no changes at the township level all

properties within in the township will receive the state

multiplier. It is applied at the County level and is called a

township equalization factor. In a perfect system if all

properties reflected the same level of assessment this can

work and no property becomes over or under assessed.

Since the Market is constantly changing this rarely takes

place except for maybe short period of time. At the

township level the assessor needs to break the DORís

Study down to a neighborhood level to monitor the

changes in the Market and make appropriate adjustments.

For example if you have one neighborhood where

property is selling according to its assessed value the

assessments may need very little adjustment or none. On

the other hand if another area is selling for more that

$10,000 over or under the estimated Market Value these

properties have to be adjusted to the proper assessment

level. Note sales must reflect market value. No it is not an

exact science but the assessment officials use market

comparison data and statically test data to do the best job


In the two examples above one can see a flat factor across

all properties will not yield the fairest results. If the

DORís tentative factor is 4% for example and the assessor
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closes the assessment changes for the township with
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only 2% adjustment. The county will be ordered by the
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DOR to apply a township equalization factor of 2% more
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