How contingency-fee appeal firms work, and when they are worth it
They take a share of the first year's saving. That is good value for some properties and poor value for others.
Most property tax appeal firms work on contingency: they file on your behalf and take a share of what you save. The model is attractive because it looks costless — no win, no fee. It is worth understanding what you are actually buying.
How the fee works
The common structure is a third of the first year's saving, sometimes half. Some firms take a share of multiple years. Read which, because the difference is large: a reduction generally holds for the whole reassessment cycle, so "first year" and "each year of the cycle" differ by a factor of three or four.
Points to check in any engagement letter:
- How is "saving" calculated? Against the original assessment, or against what the assessment would have been? These give different numbers.
- One year or the cycle?
- Is there a minimum fee that applies even on a small reduction?
- Who pays filing or appraisal costs if the case escalates?
- Does the engagement auto-renew and file on your behalf next year without asking?
What the county's record says about the value
Cook County records whether each appeal was filed by an agent or the owner. Across six tax years, the agent advantage changes sides — agents ahead in 2021 and 2024, owners ahead in 2022, 2023, 2025 and 2026. In four of six years, owners filing alone did better.
On the largest single-year sample, tax year 2024 with over 440,000 decisions, the two were within half a percentage point of each other.
The honest summary is that the county's own data shows no consistent professional advantage for ordinary residential appeals.
The arithmetic on a typical case
On a home assessed at $30,000, that is $2,520 — worth roughly $570 a year at a mid-range composite rate.
A third of that is about $190, for a filing you could have made yourself in an evening, at no cost, with no measurable difference in the odds.
When a firm is genuinely worth it
- Commercial or income-producing property. The income approach is specialist work and the sums justify it.
- A portfolio. Volume is a management problem, and someone has to actually run it.
- PTAB or litigation. That is a proceeding rather than a filing.
- You will not otherwise do it. Two thirds of something beats all of nothing, and this is a perfectly good reason — just make it a decision rather than an assumption.
The question to ask
"What is your success rate in my township, and how does it compare with the Assessor's published rate for that township?"
The county publishes the base rate, and it ranges from 30.6% in Jefferson Township to 7.6% in Palatine for the same year. A firm operating mainly in a high-rate township will show a high success rate without being any better than average. A firm that cannot answer, or that quotes a county-wide number far above the county's own, is quoting itself.
What to watch for
Unsolicited mail after a reassessment. Firms buy the roll and write to everyone whose assessment rose. The letter is not evidence you have a case.
Automatic renewal. Some engagements continue filing annually and taking a share, in years you may not have wanted to file at all.
A guaranteed reduction. Nobody can guarantee this. The county-wide success rate is 23% and falling.