Illinois Property Tax Assessment Appeal Letter Generator

If you own property in Illinois and believe your assessed value is too high, you have a legal right to appeal. Illinois assesses most property at one-third of fair market value (Cook County uses different classifications), and even small valuation errors can cost you hundreds or thousands of dollars per year. A well-drafted appeal letter to your local Board of Review or directly to the Illinois Property Tax Appeal Board (PTAB) is the first formal step toward lowering your tax bill. Because Illinois enforces strict 30-day filing windows tied to the publication of assessment lists, missing a deadline usually means waiting an entire year to try again. This page explains how Illinois assessment appeals work, what your letter should include, and the procedural rules you need to follow.

Illinois property tax law is governed by the Property Tax Code, 35 ILCS 200/1-1 et seq. Outside of Cook County, the Township or County Assessor sets a value intended to equal 33⅓% of fair cash value (35 ILCS 200/9-145). Cook County uses a classification ordinance setting different assessment levels for residential, commercial, and industrial property. After assessments are published, taxpayers may file a complaint with the County Board of Review under 35 ILCS 200/16-55. The Board of Review must accept complaints filed within 30 days of the publication date of the assessment list for that township. Common grounds for appeal include: (1) lack of uniformity—your property is assessed higher than comparable properties; (2) overvaluation—the assessed value exceeds one-third of fair market value; (3) factual errors in property characteristics (square footage, lot size, condition); and (4) recent arm's-length sale price below the implied market value. If the Board of Review denies relief or grants insufficient relief, the taxpayer may appeal to the Illinois Property Tax Appeal Board under 35 ILCS 200/16-160 within 30 days of the Board's final decision, or file a tax objection complaint in circuit court under 35 ILCS 200/23-5 after paying the disputed taxes. PTAB decisions are based on equity and the manifest weight of the evidence and are subject to administrative review. Cook County has its own preliminary appeal process through the Cook County Assessor's Office before reaching the Cook County Board of Review, with separate township-by-township filing windows announced annually.

An effective Illinois property tax appeal letter functions as both a formal complaint and a persuasive evidence package. Start by clearly identifying the property by Permanent Index Number (PIN), the tax year being appealed, and the specific assessed value you are challenging. State the legal basis—uniformity, overvaluation, factual error, or recent sale—and tie each ground to specific evidence. For a uniformity argument, attach a comparables grid showing three to six nearby properties of similar size, age, and class with lower assessments per square foot. For an overvaluation argument, include a recent appraisal, closing statement, or listing of comparable sales within the past 12-24 months and calculate the implied market value (assessed value × 3 outside Cook County). For factual errors, attach photos, surveys, or contractor estimates documenting the discrepancy. Request a specific revised assessed value rather than asking the Board to 'lower' the assessment generally—decisionmakers grant relief more readily when given a concrete number to adopt. Reference 35 ILCS 200/16-55 and the relevant assessment ratio. Sign and date the letter, include your contact information and the parcel address, and submit it through the Board of Review's required filing portal or by certified mail before the 30-day window closes. Keep proof of timely filing; Illinois boards strictly enforce deadlines and will not consider late evidence. A professional, evidence-driven letter often resolves the matter at the Board of Review level without needing to escalate to PTAB.

Board of Review filing is generally free; PTAB filing is also free for residential appeals under $100,000 in assessed value. Hearings before the Board of Review and PTAB are informal—you do not need an attorney, though one is required for corporate-owned property. Filing windows are jurisdiction-specific: each township's 30-day window opens when its assessment roll is published, so check your county assessor's website. PTAB appeals must be filed within 30 days of the Board of Review's final decision letter. Alternatively, you may file a tax objection complaint in circuit court under 35 ILCS 200/23-10 after paying taxes under protest. Small claims court is not the appropriate venue for assessment disputes in Illinois.