How to read your assessment notice
Four numbers and one date matter. The date is the one that ends your options.
An assessment notice is a dense page, most of which is procedural. Four numbers on it matter, and one date matters more than all of them.
The date first
Find the appeal deadline before you read anything else. It is usually 30 days from the publication of your township's assessment roll, and it is not extendable. A late filing ends the appeal outright — there is no cure, no discretion and no appeal against the lateness.
Diary it now. Everything else on the page can wait a week; that cannot.
The four numbers
| Field | What it is | What to check |
|---|---|---|
| Land | Assessed value of the lot | Compare against similar-sized lots nearby |
| Improvement | Assessed value of the building | This is the figure a uniformity argument uses |
| Total | Land + improvement | Divide by your ratio for implied market value |
| Prior year | Last year's figures | The size and direction of the change |
The land/improvement split is the most under-used piece of information on the page. Only one of them may be wrong, and the arguments are different. A uniformity comparison runs on the improvement figure against the building's floor area — using the total would penalise you for having a larger lot than the properties you are comparing against.
The property characteristics
Somewhere on the notice or on your parcel's page online, the county states what it thinks your property is. Check every field:
- Floor area. The most consequential number on the page. It drives the model and it is the denominator of any uniformity argument. Check it against your closing documents, a refinance appraisal, or a tape measure.
- Year built. A wrong decade puts you in the wrong comparison group.
- Bedrooms, bathrooms, basement, garage, air conditioning. A basement recorded as finished that never was is a real and common error.
- Lot size. Drives the land figure.
- Class code. Determines the assessment ratio and who you are compared against. A misclassified property is assessed on the wrong basis entirely.
The arithmetic to do in five minutes
- Implied market value. Total assessed ÷ your ratio — 0.10 in Cook, 0.3333 elsewhere in Illinois. Would you list at that price? If clearly not, you have a market-value argument.
- Your assessment per square foot. Improvement assessed value ÷ floor area. This is the number that matters for uniformity.
- Compare it. Look up three or four genuinely similar neighbours — same class, similar size, similar age, same street or block — and do the same division. If yours is conspicuously higher, that is your argument, and it does not depend on the market at all.
The exemption lines
Most notices and all bills list the exemptions applied. Read them. A missing homestead exemption is worth more than the median successful appeal in most Illinois counties, is granted on application rather than won on an argument, and is frequently missing after a change of ownership because it does not transfer from the previous owner or a builder.
If the exemption lines are empty and you own and live in the property, stop reading about appeals and go and file that application first.
What is not on the notice
Your tax bill. The notice tells you the assessed value; the bill arrives later and applies the equalisation factor, exemptions and the composite rate of every district that covers your parcel. A notice showing a 10% increase does not mean a 10% higher bill — the rate may move in either direction.