Should you appeal every year?
No. Appeal when something changed, or when you have a case you did not have before.
Not automatically, and filing reflexively every year is a good way to waste several evenings. But checking every year is worth twenty minutes, and the two are different activities.
Check annually, file selectively
The annual check is quick:
- Divide your assessed value by your ratio. Is the implied market value still plausible?
- Divide your improvement assessment by your floor area. Compare against four neighbours.
- Look at the exemption lines on your bill. Is anything missing that was there last year?
If all three look fine, you are done for the year. If one does not, that is your argument.
The years genuinely worth filing
A reassessment year. Your value was rebuilt from scratch, which is where new errors are introduced. In Cook this is every third year for your township; elsewhere in Illinois, every fourth.
After the market falls. Your assessment is carried forward between reassessments. If values dropped since the last cycle, your number reflects a market that no longer exists — and this is the situation people most often fail to notice, because nothing on the notice changed.
After a change to the property. A demolition, a fire, a partial loss, an easement, a commercial neighbour arriving.
When you discover a record error. Any year. And ask about a certificate of error, which in several counties can correct prior years too.
When your neighbours have been winning. Each reduction they obtain widens the gap between them and you, and that gap is precisely what a uniformity claim is made of.
The years usually not worth it
You won last year and nothing has changed. The reduction generally holds through the cycle. Re-filing invites a fresh look at a number you are happy with.
You bought recently for more than the implied value. Filing on market-value grounds would hand the board the evidence against you. A uniformity argument may still be available and does not require discussing your purchase price.
The gap is inside the noise. If your comparables disagree among themselves by more than the amount you are above them, you have a noisy sample rather than a finding.
The base rate to keep in mind
Across 1.79 million Cook County decisions, 23% produced a reduction — and the rate has been falling, from 31.9% in 2021 to 16.2% in 2025. It also varies enormously by township, from 30.6% down to 7.6% in the same year.
Filing every year regardless is playing a lottery with a declining payout. Filing when the arithmetic says you have a case is a considered decision with a much better expected return.
The habit worth building
When your assessment notice arrives, do the twenty-minute check and diary the deadline. Most years you will conclude there is nothing to do, and that conclusion is itself worth having — it is the difference between knowing your assessment is fair and merely assuming it.