Yes, the board can raise your assessment
It is uncommon, it is real, and it is the reason to check whether you are the low one first.
Yes. The Board of Review has the authority to increase an assessment as well as reduce it, and this surprises people who assume an appeal can only help.
It is worth understanding precisely, because the fear of it stops people filing appeals they should file, while the reality of it catches out the few who genuinely should be careful.
The two stages are different
| Stage | Can it raise your assessment? |
|---|---|
| Cook County Assessor | No — an appeal here cannot increase it |
| Board of Review | Yes — it may raise, lower or confirm |
| Property Tax Appeal Board | Yes, in principle |
That first row is why the Cook Assessor stage is close to a free option. You file, and the worst outcome is that nothing changes.
How often does it actually happen?
Rarely, for residential property. Boards are not looking for properties to increase; they are working through filings. An increase generally requires something that positively demonstrates the current value is too low — and the most common source of that something is the appellant's own evidence.
The realistic risk, stated plainly
You bought the house last year for $420,000. The county's assessment implies a value of $340,000. You file a market-value appeal, and to support it you attach your closing statement.
You have just given the board a recent arm's-length sale of the subject property at a price well above its implied value. That is the strongest evidence in the entire process, and it points against you.
This is the scenario to avoid, and it is almost the only one.
How to avoid it
Do the arithmetic before you file. Divide your assessed value by your ratio. If the implied market value is at or below what the property would realistically sell for, a market-value appeal is not your argument.
Use uniformity instead. A uniformity claim compares your assessment against comparable properties and never requires you to state what your property is worth. If you are fairly valued but unfairly assessed relative to your neighbours, this is the ground that fits — and it does not put a sale price in front of the board.
In Cook, use the Assessor stage first. No increase is possible there. You learn how the office responds to your argument at no risk, and you can decide about the Board afterwards.
What the county's own record suggests
Across 1.79 million decided Cook County Assessor appeals, the common outcomes are a reduction or no change. The Assessor stage genuinely is one-directional, which makes the decision to file there almost purely a question of whether your time is worth the expected saving.
The summary
Do not let this stop you filing. For the ordinary case — where you are not sitting on a recent purchase above the county's implied value — the risk is close to theoretical, and in Cook the first stage carries none at all. Check the arithmetic first, pick the ground that fits your facts, and do not volunteer evidence that argues the other side's case for it.