How your tax bill is actually calculated, step by step
Assessment × equalizer − exemptions × tax rate. Only one of those four is yours to argue with.
Four numbers produce your bill, and they arrive from four different places.
1. Assessed value
Set by your township assessor or county Supervisor of Assessments. Roughly one third of what they believe the property would sell for. This is the only one you can appeal.
2. The equalization factor
A county-wide multiplier from the Department of Revenue, correcting the county's overall assessment level toward 33⅓%. Applied to everyone equally.
3. Exemptions
Subtracted after equalization. The general homestead exemption, senior exemptions, the senior assessment freeze, veterans' exemptions and the home improvement exemption all reduce the taxable figure. Missing one is common and is worth checking before you appeal anything.
4. The tax rate
Not a rate anyone chooses directly. Each taxing body — school district, municipality, park district, library, county — adopts a levy, a dollar amount it needs. The clerk divides the total levy by the total equalized assessed value in the district. That quotient is your rate.
The order
((Assessed × Equalizer) − Exemptions) × Rate = your bill. Schools typically take the largest share.
The consequence people miss: because the levy is fixed first and the rate is derived from it, a successful appeal does not reduce the money collected. It moves your share onto everyone else — which is exactly what happens to you when your neighbour is under-assessed.