Illinois Property Tax Appeals — The Complete Guide
Last reviewed: May 2026 · Tax year covered: 2025 (billed 2026), 2026 (billed 2027) · Sources: IL DOR (PIO-74), 35 ILCS 200/, IL PTAB published decisions, county Supervisor of Assessments offices
Cook County readers: the property tax system in Cook (Chicago + suburbs) differs materially from the rest of Illinois — assessment ratio, reassessment cycle, appeal venues, and exemption amounts are all different. Use this page for the framework, but follow Cook-specific guidance for procedure.
The 30-second answer
Illinois residential property is assessed at 33⅓% of fair market value in every county except Cook (where it's 10%, by ordinance).
You have 30 days after your township's assessment roll publishes to file a formal appeal at your County Board of Review. This deadline is almost always fatal if missed.
Most appeals win or lose on 3-5 comparable sales within 12 months of the January 1 assessment date — same neighborhood, same size/age/style. Boards reject appeals where comps don't match.
Appeal escalates: Township Assessor → County Board of Review → IL PTAB (or Circuit Court). PTAB decisions take 1-3 years.
The hidden lever most homeowners miss: if you win at PTAB on an owner-occupied home, Section 16-185 carries the reduction forward for the rest of the general assessment period (often 3 more years).
Quick facts: Illinois property tax appeals
Statewide framework. Cook is the exception to most of these rules — see Cook section.
Metric
Value
Statutory residential assessment ratio
33⅓% of fair market value (Cook uses 10% — see Cook section)
Statewide median effective tax rate
~2.07% (4th highest in the U.S.)
General reassessment cycle
Every 4 years for most counties (Cook is triennial-by-district)
Appeal escalation path
Township Assessor → County BoR → PTAB or Circuit Court
BoR appeal window
30 days after the township's assessment roll publishes
PTAB filing window
30 days from the BoR's final decision
Burden of proof — market-value appeals
Preponderance of evidence (>50%)
Burden of proof — uniformity appeals
Clear and convincing (substantially higher)
Owner-occupied PTAB rollover
35 ILCS 200/16-185 — reduction carries through general assessment period
How Illinois property tax assessments actually work
Two things can be wrong with your assessment: the implied market value, or the relative assessed value vs. neighbors. Both are appealable, with different rules.
Illinois law sets the assessment ratio at 33⅓% of fair market value in every county except Cook (35 ILCS 200/9-145). The Illinois Department of Revenue applies an annual state equalization factor ("the multiplier") to keep counties aligned with the statutory ratio.
The math (non-Cook counties):
Tax bill = (Assessed Value − Exemptions) × State Equalization Factor × Local Tax Rate
Two appealable error types:
Market-value overstatement — the assessor's implied market value is higher than what comparable homes are actually selling for. Most common appeal basis. Lower burden of proof.
Uniformity (equity) — other homes in your neighborhood with similar characteristics are assessed at lower values. Different argument with different evidence rules. Higher burden of proof.
⚠️ Township vs. commission-form counties. Most of Illinois uses a township system: each township has its own elected assessor. The 30-day appeal window keys to your township's roll publication date, which can vary by weeks within the same county. Cook and a few small downstate counties have no townships — the County Assessor handles all valuations directly.
How Illinois reassessment timing actually works
Three distinct mechanics affect your assessed value over time. They run independently and can each change your bill in any given year:
General/system-wide reassessment. Most Illinois counties operate on a four-year quadrennial cycle — every parcel in the county gets reassessed in the same calendar year, simultaneously, by the township assessor's mass-appraisal process. Cook County is the exception: its reassessment runs triennially by district (City of Chicago, North Suburbs, South & Southwest Suburbs in rotation), so different parts of the county hit reassessment in different years. Most of DuPage's last general reassessment was 2023; the next is scheduled for 2027. Other counties run on similar four-year cycles offset by their own schedules.
Mid-cycle individual reassessment. Unlike acquisition-value states (such as California under Prop 13), a change of ownership alone does not trigger reassessment in Illinois — sale prices are not automatically substituted for the assessor's valuation. However, individual parcels can still be reassessed mid-cycle for: new construction (additions, finished basements, new structures), demolition or removal, factual record corrections (square footage error, demolished features still listed, lot size correction), and post-PTAB §16-185 rollover (a successful owner-occupied appellant can carry forward their reduced assessment, with separate petitions filed for each remaining year of the general assessment period). An ownership change can be the occasion for an assessor's review that uncovers other reassessment-worthy items, but the change itself isn't the trigger.
Annual mechanisms between reassessments. Even in non-reassessment years, three distinct mechanisms can shift your taxable value: township equalization factors (the County Supervisor of Assessments adjusts within-county township-to-township ratios annually), state equalization multipliers (the IL Department of Revenue applies a county-level multiplier to bring assessed values into alignment with the statutory 33⅓% ratio statewide), and caps & freezes that protect specific homeowners — most notably the Senior Citizens Assessment Freeze ($75,000 household income cap for 2026), which freezes Equalized Assessed Value at base-year levels for qualifying seniors. These mechanisms produce annual bill changes (DuPage's 2025 roll showed an 8.2% AV increase even though it wasn't a general reassessment year) without triggering a full reassessment.
Should you consider appealing?
If any of the green-checked items below applies to your situation, taking 5 minutes to look closer is worth it. The red items aren't appeal grounds.
✅ Reasons to look closer
Your assessed value (×3 in non-Cook, ×10 in Cook) implies a market value above recent nearby sales of similar homes
You recently bought the home for less than the assessor's implied market value
Your property record has factual errors (sq ft, beds, baths, year built, demolished features still listed, lot size)
Your assessment jumped more than your neighbors' between cycles
A nearby comparable home is assessed lower despite similar size, age, condition
❌ NOT valid appeal grounds
The bill is "too high" in absolute dollars
Taxes went up year-over-year (when caused by the rate or new levies, not the assessment)
General fairness arguments without supporting evidence
Disagreement with how the local tax rate is set (that's a levy dispute, not an assessment dispute)
📋 Your move: Pull your property record from your county's online lookup. Compare the listed sq ft, bed/bath count, lot size, and year built to your actual home. Factual errors are the easiest, lowest-cost appeals — most can be corrected by the township assessor without a formal BoR filing. Also confirm all exemptions you qualify for — claiming a missed Senior Freeze or Disabled Veterans' Homestead is often a larger lever than an assessment-level appeal.
Cost of appealing in Illinois
Illinois Boards of Review generally do not charge filing fees for residential appeals — appealing at the county BoR level is procedurally free. The real costs are:
Time commitment (DIY): typical 5-10 hours pulling 3-5 comparable sales, photographing, completing the appeal form, and preparing supporting documentation
PTAB escalation: also no filing fee for residential pro se appellants; PTAB published rules govern
Professional fees (optional): licensed Illinois property tax consultants and attorneys typically charge 25-35% contingency on one year's tax savings (some demand higher); flat-fee arrangements ($300-$1,500) exist but are less common
Appraisal (optional, used in stronger cases): an Illinois-licensed appraiser dated as of January 1 of the assessment year typically runs $400-$800 for residential — strongest single piece of supporting evidence when the cost makes sense
Risk of appealing. PTAB and county BoRs in Illinois cannot raise your assessment as a result of a residential appeal — the worst-case outcome is a denial leaving the assessment unchanged. There is no "punitive reassessment" risk for filing a good-faith protest.
The Illinois three-tier appeal process
Same escalation path statewide. Each tier has a 30-day deadline. Most homeowners stop at Tier 1 or 2.
1
Township Assessor
Informal review · No statutory deadline (before formal cutoff)
Contact your township assessor's office. They'll review your record and your comparables informally. Many cases resolve here, especially when the issue is a factual data error.
Lowest-cost step. Start here.
2
County Board of Review
Formal appeal · 30 days after township roll publishes
If the informal review doesn't resolve it, file a formal appeal. Most counties require 3-5 comparable sales, photographs, and original signatures. Decisions typically issued months later.
Hard deadline. Miss it = wait until next year.
3
PTAB or Circuit Court
State escalation · 30 days from BoR decision
PTAB = administrative, no attorney required, decisions take 1-3 years. Circuit Court = judicial, attorney typically required, faster but more expensive. You can't pursue both.
PTAB is the more common DIY route.
⚠️ Corporate appellants must be represented by an Illinois-licensed attorney at every tier. Individual homeowners can file pro se throughout. Most counties also prohibit filing by fax or email; specific procedural rules vary by county, and each county's BoR rules should be confirmed before submitting.
What evidence Illinois Boards of Review actually accept
Most DIY appeals fail on evidence, not on merit. The rules are largely standardized statewide. Match them exactly.
✅ What you need to submit
For market-value appeals:
3-5 comparable sales (not more than 5)
Each comp's sale price, sale date, descriptive data, photograph
Comps within 12 months of January 1 assessment date
Comps similar in size, construction, age, style, condition
Comps in the same neighborhood/subdivision (or explanation if not)
Acceptable documentation:
MLS listing sheet
Sales contract + closing statement
Appraisal by IL-licensed/certified appraiser dated Jan 1
Builder's contractor affidavit (new construction)
For uniformity appeals:
3-5 comparable assessed properties (not sales)
Summary table: each comp's assessed value vs. yours
❌ Common reasons appeals get dismissed
Fewer than 3 comps, or more than 5
Comps outside the 12-month window
Comps in a substantially different neighborhood without explanation
Missing required photographs or documentation
Filed by fax or email where prohibited
Missing original signatures
Corporate appellant without attorney representation
Missing the 30-day filing window (almost always fatal)
Mixing market-value and uniformity arguments without picking one
💡 Choose one theory and frame the evidence around it. Market-value and uniformity appeals are different theories with different burdens of proof. Mixing them often weakens both. When evidence supports both arguments, market value tends to be the stronger lead — its lower burden of proof (>50%) is meaningfully easier to meet than uniformity's "clear and convincing" standard.
What actually wins and loses at PTAB
We read 8 published PTAB decisions for DuPage residential properties (2022-2024) to identify what evidence patterns succeed. The rules apply statewide — only the underlying properties happen to be in DuPage.
1 reduction (won on legal mechanism)
5 upheld (failed on comp-sales evidence)
2 settled pre-hearing
The 4 reasons appeals lose at PTAB
1
Comparable sales too old
The #1 reason. PTAB downweights any comp sold >12 months from the January 1 assessment date.
2
Comps that aren't really comparable
Differences in size, age, design, basement, lot size, bath count all trigger weight adjustments.
3
The BoR's evidence is stronger
In 4 of 5 losing decisions, PTAB found the BoR's comps to be "best evidence of market value" — not the appellant's.
4
Uniformity is harder to win
The "clear and convincing" burden trips up appellants whose comps lack an exact feature match (basements are the common one).
Pattern 1 detail — comparable-sales recency
In 5 of 5 "No Change" decisions, PTAB explicitly downweighted comparable sales too far from the January 1 assessment date:
"The Board gives less weight to the appellant's comparable #3 ... due to their sale dates occurring greater than 15 months prior to the January 1, 2022 assessment date at issue." — Golewale (Milton Twp), Docket 22-03618
Sales 15+ months out are routinely discounted. PTAB applies the 12-month rule more rigidly than many county BoRs.
Basement (finished vs unfinished is a major weight factor)
Lot size
Bathroom count, fireplace count, garage size
Multiple losing decisions noted appellant comparables "lack[ed] finished basement area, which is a feature of the subject" or were "significantly smaller than the subject dwelling."
Pattern 3 detail — BoR usually outguns the appellant
In 4 of 5 losing decisions, PTAB found "the best evidence of market value" to be the Board of Review's comparables, not the appellant's. The BoR has access to the same MLS data and often submits more recent or more dimensionally similar comps.
Practical takeaway: plan to submit 5 strong comparables (not the rule-minimum 3), each within 12 months and closely matched on size/age/design/basement. Anticipate a BoR counter-package of 4-5 comps supporting the existing assessment.
Pattern 4 detail — uniformity burden of proof
86 Ill. Adm. Code 1910.63(e) sets two different burdens:
Market-value: preponderance (>50%)
Uniformity: clear and convincing (substantially higher)
In our sample, the uniformity case (Goworowski, Lisle Twp, Docket 24-04149) lost because 4 of 6 appellant comps lacked the finished basement feature of the subject — failing the higher equity standard.
If you have both arguments, lead with market value.
up to $75,000 market value (~$25,000 EAV), 4 years
New residential improvements
Long-Time Occupant Homestead(Cook only)
Variable
10+ years continuous occupancy, income ≤ $100,000
⚠️ Senior Freeze annual recertification. Most exemptions auto-renew once granted. The Senior Freeze does not — it requires annual income recertification. Missing the deadline is one of the most common preventable losses for Illinois seniors. The income cap rises to $77,000 for 2027 and $79,000 for 2028.
📋 Your move: Confirm with your township assessor's office which exemptions are currently applied to your parcel. A senior homeowner outside Cook with income under $75,000 should hold the GHE ($6,000-$8,000), Senior Homestead ($5,000), and Senior Freeze simultaneously. If any are missing, exemption stacking is often a larger lever than an assessment-level appeal.
Major Illinois counties
10 most populous counties covered. Click your county to expand. Cook is structurally different from the rest — read the Cook section even if you don't live there for context.
Cook County · pop. 5.1M · Chicago + suburbs · structural exception
Population: ~5,100,000
Townships: none — County Assessor
Assessment ratio: 10% (classification ordinance)
Reassessment cycle: Triennial by district
Exemption tier: Highest (Cook-only LTOH)
Appeal venue: Cook County BoR (3 commissioners)
Cook is the exception to almost everything else on this page. It's the only Illinois county that operates under a classification ordinance rather than the statutory 33⅓% ratio — residential is assessed at 10% of market value, commercial at 25%. The IL Department of Revenue applies a Cook County equalization multiplier (typically ~3.0×) to bring effective taxable value into alignment with the rest of the state.
Reassessment runs on a triennial cycle by district: City of Chicago in one year, North Suburbs the next, South & Southwest Suburbs the year after, then repeat. Your reassessment year depends on which district your home is in.
From BoR, escalation goes to PTAB or Circuit Court as elsewhere
💡 Cook-specific exemptions. Higher GHE ($10,000) and Senior Homestead ($8,000) than the rest of the state. Plus the Cook-only Long-Time Occupant Homestead Exemption for 10+ year continuous owner-occupants with income ≤ $100,000.
DuPage County · pop. 932K · west suburbs · 9 townships
Population: ~932,000
Townships: 9
Assessment ratio: 33⅓%
Next general reassessment: 2027
Exemption tier: Higher (contiguous to Cook)
Appeal venue: DuPage County BoR
DuPage uses the standard 9-township system with a 33⅓% assessment ratio and follows the standard four-year general reassessment cycle. The 2025 assessment roll (billed in 2026) reflected an 8.2% jump in assessed values offset partially by a 4.37% tax rate decline — a net 3.83% bill increase.
Appeals: township assessor → DuPage County Board of Review → PTAB or Circuit Court. The 30-day formal appeal window runs from each township's roll publication date; in 2025, lead townships published October 16.
The DuPage BoR's Rules of the Board of Review are widely cited as a representative model of Illinois county BoR procedure (Rule 9 for residential market-value evidence, Rule 1 for procedural-failure dismissal).
📋 Your move: A dedicated DuPage County deep-dive page is coming soon with the full 9-township assessor directory, contacts, and current-year deadlines.
Lake County · pop. 715K · north suburbs · 18 townships · highest absolute tax bills
Population: ~715,000
Townships: 18
Assessment ratio: 33⅓%
Reassessment cycle: 4-year general
Exemption tier: Higher (contiguous to Cook)
Appeal venue: Lake County BoR
North of Cook along the Wisconsin border — Waukegan, Highland Park, Lake Forest, Gurnee, Buffalo Grove. Encompasses both the affluent North Shore corridor and fast-growth western Lake. Lake's median property tax bill is among the highest in Illinois — North Shore parcels routinely produce absolute tax bills well into five figures.
💡 Economics-of-appeal note. Lake's high absolute tax dollars mean even modest percentage reductions are worthwhile. A 5% reduction on a $20,000 bill recoups 50+ DIY hours easily — and Section 16-185 rollover compounds that across the assessment period.
Will County · pop. 696K · south suburbs · 24 townships · I-55 reassessment shocks
Population: ~696,000
Townships: 24 (one of largest in IL)
Assessment ratio: 33⅓%
Reassessment cycle: 4-year general
Exemption tier: Higher (contiguous to Cook)
Appeal venue: Will County BoR
South-southwest of Cook — Joliet, Bolingbrook, Plainfield, Romeoville, Lockport. Anchors the I-55 / I-80 fast-growth corridor. With 24 townships, publication-date variance is wider than in smaller counties — confirm your specific township's window before relying on a county-aggregate date.
⚠️ Reassessment shocks. Will experienced substantial 2024-2025 reassessment increases in the I-55 corridor (Plainfield, Bolingbrook) where new-construction comps were aggressive during the post-2020 housing peak. The BoR has often had robust counter-comp packages prepared in those townships. Plan to submit 5 comps, not 3, with closing-statement-grade documentation.
Kane County · pop. 516K · west suburbs · 16 townships · farmland-residential mix
Population: ~516,000
Townships: 16
Assessment ratio: 33⅓% (residential) + Use Value (farmland)
Reassessment cycle: 4-year general
Exemption tier: Higher (contiguous to Cook)
Appeal venue: Kane County BoR
Far western suburbs along the Fox River — Aurora, Elgin, Geneva, St. Charles, Batavia. Mix of dense Fox River-corridor residential, suburban subdivisions, and substantial agricultural land in western/northern townships.
⚠️ Hybrid residential + farmland parcels. Significant portions of western/northern Kane are assessed under the Use Value (PTAX-227) farmland system — a separate framework outside the residential 33⅓% ratio. If your parcel mixes residential structures with farmland acreage, the appeal mechanics differ on the farmland portion. Farmland is appealed on use value (productivity factors set annually by the IL Department of Agriculture), not market value.
North-northwest of Cook between Lake County and the Wisconsin border — Crystal Lake, Woodstock, Algonquin, McHenry city, Huntley, Cary. Housing stock is bimodal in age: Huntley/Algonquin/Lake-in-the-Hills skews 1990s-2010s tract construction, while western townships include substantial pre-WWII farmhouses and small-town residential.
💡 Comp-similarity matters more here. A 1995-built tract home in Huntley and a 1920s farmhouse two townships west are not interchangeable comps. Even within the same township, design-era differences (split-level vs ranch vs two-story) produce significant PTAB weight adjustments. Choose comps within ~10 years of your subject's age, not just within the same neighborhood.
Madison County · pop. 261K · downstate Metro East · 24 townships · lower-tier exemptions
Population: ~261,000
Townships: 24
Assessment ratio: 33⅓%
Reassessment cycle: 4-year general
Exemption tier: Lower ($6,000 GHE, $5,000 Senior)
Appeal venue: Madison County BoR
Downstate Metro East across the Mississippi from St. Louis — Edwardsville (county seat), Granite City, Alton, Collinsville, Glen Carbon. Anchors the Illinois side of the St. Louis metropolitan area.
Median home values run ~one-third of DuPage's. Absolute property tax bills typically $2,000-$4,500 (vs DuPage $7,800+).
💡 DIY tilts harder at lower bill levels. Percentage savings on successful appeals are comparable statewide because the evidence framework is identical. But a 33% contingency on $400 of annual savings is rarely worth losing the Section 16-185 rollover work that most service companies don't pursue. Madison residents should confirm exemption stacking (GHE + Senior + Senior Freeze where eligible) before assuming an assessment-level appeal is the right lever.
St. Clair County · pop. 258K · downstate Metro East · 22 townships · Scott AFB
Population: ~258,000
Townships: 22
Assessment ratio: 33⅓%
Reassessment cycle: 4-year general
Exemption tier: Lower ($6,000 GHE, $5,000 Senior)
Appeal venue: St. Clair County BoR
Downstate Metro East south of Madison — Belleville (county seat), East St. Louis, O'Fallon, Fairview Heights, Swansea. Hosts Scott Air Force Base in the eastern townships, which makes the veterans' exemption layer materially more relevant here than in most counties.
📋 Veterans' exemptions are underutilized here. Returning Veterans' Homestead Exemption ($5,000 for one tax year following return from active armed-conflict duty) and Disabled Veterans' Standard Homestead Exemption ($2,500 / $5,000 / fully exempt by disability rating) can stack with GHE + Senior. If you've recently separated or are receiving VA disability compensation, file the exemption paperwork at the township level before pursuing an assessment appeal — it's often the larger lever.
Champaign County · pop. 206K · central IL · 30 townships · UIUC student-rental quirk
Population: ~206,000
Townships: 30 (largest count of these 10)
Assessment ratio: 33⅓%
Reassessment cycle: 4-year general
Exemption tier: Lower ($6,000 GHE, $5,000 Senior)
Appeal venue: Champaign County BoR
Central Illinois — Champaign, Urbana, Rantoul, Mahomet, Savoy. Home of the University of Illinois at Urbana-Champaign, which dominates the local housing economy through both direct university housing and a substantial private student-rental market.
⚠️ GHE eligibility for student-rental properties. The General Homestead Exemption requires the property to be the owner's primary residence. Properties used primarily as student rentals don't qualify, even if the owner occupies them seasonally. Champaign-Urbana homeowners with ambiguous occupancy status (faculty who rent rooms, owners who summer there but rent during the school year) should confirm eligibility before relying on GHE — mistaken claims that the assessor later reverses produce supplemental bills covering multiple back years.
Winnebago County · pop. 284K · Rockford metro · 14 townships · uneven post-2020 recovery
Population: ~284,000
Townships: 14
Assessment ratio: 33⅓%
Reassessment cycle: 4-year general
Exemption tier: Lower ($6,000 GHE, $5,000 Senior)
Appeal venue: Winnebago County BoR
Far northern Illinois along the Wisconsin border, anchored by Rockford. Major cities: Rockford, Loves Park, Machesney Park, Cherry Valley, Roscoe, Rockton.
Rockford metro experienced a long flat housing-price period through the 2010s followed by substantial post-2020 recovery, producing reassessment patterns that lag the rest of the state.
💡 Sub-neighborhood comp segmentation. Because Rockford-area home prices were flat for so long before the 2020-2024 run-up, assessor-implied market values can be misaligned in either direction — overestimating in neighborhoods where the recovery hasn't fully landed, underestimating in fast-recovering areas. The same Rockford ZIP can include both blocks where 2024 sales run 30% above 2019 levels and blocks where they're flat. Pull comps carefully and segment by sub-neighborhood, not township-as-a-whole.
Recent Illinois context (2026)
Three things to know about the current landscape: Senior Freeze income cap rose, 2024-2026 reassessment shock wave is still propagating, and PTAB caseload remains heavy.
Senior Freeze income cap raised to $75,000 for assessment year 2026 (Public Act 103-0009). Rises to $77,000 for 2027 and $79,000 for 2028. Annual income recertification still required — missing the renewal is one of the most common preventable losses for IL seniors.
2024-2026 reassessment shock wave. Counties that completed general reassessments in 2023-2025 reflected the post-2020 housing run-up at full force, producing assessed-value increases of 8-15% in many townships. DuPage's 2025 roll: +8.2% AV, −4.37% rate, net +3.83% bill. Will and Lake counties along the I-55 and Tri-State corridors saw larger swings in fast-growth townships.
Cook 2024 City of Chicago triennial reassessment completed 2024-2025 with substantial increases in Lakeview, Logan Square, Pilsen, and other gentrifying neighborhoods. North Suburbs are now in their reassessment year (2025-2026).
General reassessment calendar. Most non-Cook counties are mid-cycle. Next general reassessment year is 2027 for many (including DuPage).
PTAB caseload remains heavy — final decisions taking 1-3 years from filing. The backlog is one reason Section 16-185 rollover relief is valuable: a single successful appeal locks in savings for the rest of the assessment period without re-litigating each year.
Frequently asked questions
Click each question to expand.
My assessor said my market value is X but I think it's lower. How do I prove it?
Pull 3-5 recent sales of similar homes within 12 months of the January 1 assessment date and within your neighborhood. Document each with sale price, date, descriptive data (sq ft, beds, baths, year built), and a photograph (MLS listing sheets satisfy this). If your home itself sold within the past 12 months for less than the assessor's implied market value, that single sale is often the strongest evidence in any Illinois county.
Can I appeal if I think my property record has factual errors (wrong sq ft, wrong bed count)?
Yes — start at the township level (or county level in Cook). Many factual errors can be corrected by the assessor without needing to escalate to the Board of Review. Bring documentation: original purchase listing, builder's specifications, photos.
Do I need a lawyer to appeal in Illinois?
No, individual residential homeowners can file pro se at every level — township, Board of Review, and PTAB. Corporate property owners must be represented by an Illinois-licensed attorney. Most residential homeowners DIY the township and BoR levels; attorneys become more common at PTAB or Circuit Court, but PTAB explicitly accommodates self-representation.
What's the difference between Cook and the rest of Illinois?
Cook uses a classification ordinance (10% residential vs. 33⅓% statewide), runs reassessment on a triennial-by-district cycle (vs. four-year general), uses a single County Assessor (no township assessors for valuation), and has its own three-commissioner Board of Review. Cook also has higher GHE/Senior amounts and the Long-Time Occupant Homestead Exemption that the rest of the state doesn't get. From PTAB upward, the procedures are identical.
My township's deadline already passed. Can I still appeal?
Not for that tax year through the Board of Review. You can file for the following assessment year when the next 30-day window opens after your township's roll publishes. If the BoR has already issued a decision on a parallel filing for that year, you have 30 days from the BoR notice to escalate to PTAB.
How long does the appeal process actually take?
Township-level informal review typically resolves within weeks if it's going to resolve at all. County Board of Review formal appeals tend to take several months — most decisions for the larger counties (DuPage, Lake, Will, Cook) are mailed the following March after a fall filing window. PTAB administrative appeals are slower — current published timelines suggest 1-3 years from filing to final decision, with backlog conditions extending some cases further. Circuit Court timelines vary substantially by county and case complexity.
What happens if I win the appeal?
Your assessed value (and therefore your tax bill, when calculated) drops accordingly. Refunds for tax years already paid generally aren't issued automatically — you may need to apply through the County Treasurer's office for a refund of overpayment for the affected tax year. For owner-occupied residences that win at PTAB, the reduced assessment tends to carry forward through the rest of the general assessment period under Section 16-185, though township equalization can still apply on top — see the FAQ below on whether the reduction lasts.
What happens if I lose the appeal?
Your assessment stays at its current level — the loss does not increase your assessed value (Illinois BoRs and PTAB cannot raise the assessment as a punitive consequence of an appeal). You can re-appeal in the next assessment year if circumstances change (new comps, new factual evidence, or a general reassessment that resets values). If you lost at the BoR level, you have 30 days to escalate to PTAB or Circuit Court for that same tax year.
What are the risks of appealing?
The financial risk in Illinois is generally low: BoR and PTAB cannot raise your assessment as a result of a residential appeal. The real costs are time (5-10 hours typical for DIY) and, if you hire a service company, contingency fees (commonly 25-35% of one year's tax savings — read the contract for auto-renewal terms). A weaker risk: filing a poorly-supported appeal can establish a record that the assessor's value is well-documented, potentially making future appeals harder if circumstances haven't changed. Most homeowners who file good-faith appeals with strong comp evidence face no meaningful downside.
If I win at PTAB, does the reduction carry forward to future years?
For owner-occupied residences, generally yes — Section 16-185 of the Illinois Property Tax Code requires the reduced assessment to carry forward for the remainder of the general assessment period, subject to township equalization being applied on top. You may need to file a follow-up "rollover" appeal each subsequent year if the township re-raises your assessment unequally. Many service companies don't pursue these follow-ups, so this is often a homeowner-initiated lever.
Service companies operating in Illinois
Service companies don't have access to better evidence than you do — they use the same MLS data. Read auto-renewal language carefully and ask about Section 16-185 rollover follow-ups.
The Illinois service-company landscape includes Ownwell (national, 25-35% contingency, with documented auto-renewal patterns generating BBB complaints), AppealDesk, a growing footprint from Texas-based O'Connor, and a long tail of local solo consultants — many of which mail flyers after a reassessment. Local-flyer consultants typically charge 33%+ contingency of one year's savings.
The underlying work — pulling 3-5 MLS-documented comparable sales within 12 months of January 1 — is something Illinois Boards of Review and PTAB will accept from any appellant equally. They don't favor represented appellants.
💡 Ask the right question. If you do hire, ask explicitly whether the firm will file a Section 16-185 rollover appeal in the year following a successful PTAB win. Most do not — despite it being a continuing-savings lever specific to Illinois owner-occupied homes that compounds the value of any reduction across the rest of the assessment period.
For the cross-state economics of DIY vs. hire (time, fee structures, when each route makes sense), see our DIY vs. hire decision matrix (coming soon).
Individual county Supervisor of Assessments / Chief County Assessment Office sites linked in each county subsection
Methodology. This page synthesizes Illinois statutory law, PTAB administrative rules, county Board of Review procedural rules (with DuPage as the representative model), and full-text reading of 8 published PTAB decisions for residential properties (DuPage, tax years 2022-2024). State-level evidence-weight patterns identified across the sample were cross-checked against PTAB's published annual synopses for consistency.
What we don't claim. This page is general orientation about how the Illinois property tax appeal system works. It is not legal advice, not a recommendation about whether to appeal a specific assessment, and not a guarantee that following these patterns will produce a favorable outcome in any particular case. County rules, deadlines, and contact information change annually — always verify current details on the linked county sites before submitting documents. For case-specific advice, consult your township assessor, the county Supervisor of Assessments office, or a licensed Illinois property tax consultant or attorney.
Related topic explainers
Cross-state explainers covering universal homeowner questions, with state-specific nuance where it matters.
For property tax terminology used in this guide (assessment ratio, equalization rate, lien date, USPAP, etc.), see the property tax glossary.
The Property Tax Desk (propertytaxdesk.com) publishes editorial guidance grounded in primary state and county sources. We do not file appeals on your behalf, do not earn commissions from service companies, and do not collect leads. Coverage limited to: Texas, California, Illinois, New Jersey, New York (additional states forthcoming).