I don't know the specifics of your state's laws, but I am curious about when the last assessment of the property was made. You included a lot of information, but not that bit.
If it hasn't been assessed for almost 5 years, and was due to be reassessed anyway, your filing for reassessment may have been all they needed to simply apply it early. Saves them doing it twice in the same year, perhaps.
Or, maybe the rules are different since YOU requested the assessment.
I'm not sure how your county/state assesses property, but I'd have wanted to know that information prior to filing for reassessment. Particularly if you knew that you paid more than the comps. The housing market is slowly making some gains in some areas, and whatever the assessment tools are, it makes sense to me that whatever you JUST paid for the property would be it's value. A home that hasn't recently been sold/purchased must use comparables, b/c that is all there is to go on... what a comparable home would bring at sale. There's no need to guess on your house... you just settled that when you made the purchase.
I'm sorry your taxes jumped.
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It only took me one google search to find the rules:
(from http://tax.illinois.gov/publications/localgovernment/ptax...)
"Reassessments
By law, each property, other than farmland, must be viewed, inspected, and revalued once every four years (every three years in Cook County). Farmland is reassessed each year. Between these general assessments, assessors may revalue property if its value is incorrect.
..."
I'd place the emphasis of that excerpt on the second sentence, where it says they can revalue it, if it's incorrect. You brought it to their attention.
Property tax is basically a direct correlation to "market price"... which in your case would be the sales price you just paid. Assessed value is 1/3 the market value, plus some minor tack on by the state.. some sort of "equalizing" function that has something to do with farmland or something.
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I wonder if you would clarify something. You said, "I filed and presented properties that were comparable and paid less tax. " What do you mean by comparables? Did you pull up homes that recently sold (within the last 3 months, or 6 months or what?) that were of similar square footage, property size, amenities and location? Or just similar sales price? Or did you look for similar homes to yours that paid less tax only, without regard for the date of the last assessment or their sales price?
Trying to pin down your reference there is bothering me. I wonder if your comparables (if they were in fact recent sales) just haven't been reassessed recently. And perhaps those will be going up as well in short order...