Do you need a lawyer to appeal your property taxes?
For a house, usually not. For a corporate-owned property at PTAB, usually yes.
For an ordinary residential appeal in Illinois: no. And unusually, this is a question the county's own records can answer rather than a matter of opinion.
What the data says
The Cook County Assessor records whether each appeal was filed by an attorney or agent, or by the owner. Across 1.79 million decided appeals:
| Tax year | Filed by an agent | Filed by the owner | Who did better |
|---|---|---|---|
| 2021 | 33.0% | 25.0% | agent, by 8.0 |
| 2022 | 24.6% | 25.8% | owner, by 1.2 |
| 2023 | 20.9% | 23.1% | owner, by 2.3 |
| 2024 | 21.3% | 20.9% | agent, by 0.4 |
| 2025 | 15.7% | 18.5% | owner, by 2.8 |
| 2026 (partial) | 17.6% | 23.6% | owner, by 6.0 |
In four of six years, owners filing for themselves did better. The advantage changes sides, which means any single-year figure — in either direction — is quoting the year that suits the argument.
The honest reading: on this evidence, professional representation shows no consistent advantage in ordinary Cook County appeals.
What it costs
Appeal firms generally work on contingency, commonly taking a third of the first year's saving, sometimes half. The median successful Cook appeal reduces assessed value by 8.4%, worth roughly $570 a year on a typical home at a mid-range rate. A third of that is about $190.
You are paying that for an advantage the county's own record cannot reliably detect.
When help is genuinely worth it
None of this applies evenly. Get professional help when:
- The property is commercial or income-producing. The income approach turns on rent rolls, vacancy and capitalisation rates. This is specialist work and the amounts are large.
- You are going to PTAB or to court. That is a proceeding, not a filing.
- You hold a portfolio. Volume is a management problem somebody has to actually run.
- The facts are genuinely complicated — a partial demolition mid-year, a contested classification, a property straddling jurisdictions.
- You will not otherwise do it. A third of something beats all of nothing, and this is a perfectly reasonable reason.
The question to ask any firm
What is your success rate in my township, and how does it compare to the Assessor's published rate for that township?
The county publishes the base rate — and it varies enormously, from 30.6% in Jefferson Township to 7.6% in Palatine for tax year 2024. A firm claiming to beat it should be able to say by how much, in a way you can check. A firm quoting a county-wide figure far above the county's own published number, without explaining the difference, is quoting itself.
What to do instead
For a residential appeal: file it yourself at the Assessor stage. It is free, it cannot raise your assessment there, and the evidence shows no reliable professional edge. Spend the effort you would have spent choosing a firm on assembling four genuinely tight comparables instead — that is the part the decision record shows actually moves outcomes.