Your assessment stayed flat and your bill still went up. Here is why
The levy moved, or the base shrank, or an exemption fell off. None of those are visible on your assessment notice.
Your assessment is one of four inputs. Three others can move without it.
A taxing body raised its levy
Your school district, village, park district or library asked for more money this year. The rate is derived from the levy, so the rate rises and so does your bill. This is the most common cause and it has nothing to do with your property.
The tax base shrank
Same levy, fewer or lower assessments to spread it across, higher rate for everyone left. A large commercial property winning a big appeal, or a TIF district capturing growth, can do this.
An exemption fell off
The most fixable cause and the easiest to miss. Senior exemptions often require annual renewal. Homestead exemptions can drop after a title change, a refinance recorded oddly, or a death in the family. Compare last year's bill to this year's, line by line, and look at the exemption block first.
Your assessment did move, slightly
An equalization factor above 1.0 raises your equalized value even when the assessor changed nothing. Check whether the number you are comparing is the assessed value or the equalized assessed value.
What to do
Put the two bills side by side and find which of the four inputs changed. If it was the rate, an appeal will not help this year and the fight is at your taxing bodies' budget hearings. If it was an exemption, call the assessor — that is a form, not an appeal.