What evidence do you need to win a property tax appeal

Last updated 2026-07-09

Why evidence is the only thing that actually matters at a hearing

Most homeowners walk into an appeal board and say some version of "this feels too high." That argument loses every time. Board members can't lower your assessment because you're upset, because your neighbor paid less, or because your bill jumped 20 percent. They can only act on evidence that your property's assessed value is wrong under the standard their state uses.

States assess at either full market value or a fixed percentage of it. California caps annual increases under Proposition 13 and uses your purchase price as the base ^[1]. Most other states aim for full market value. Either way, the assignment is the same: prove the assessor got the number wrong, and prove it with documents.

Here's the part contingency firms don't advertise. You don't need a lawyer. You don't need someone taking 30 to 40 percent of your savings. You need the right paperwork, organized cleanly, presented in the order the board expects. This guide tells you exactly what that paperwork is.

What are comparable sales (comps) and why do they win most appeals?

Comparable sales, or "comps," are records of what similar homes near yours actually sold for during the window the assessor used to set your value. Most assessors pick a "valuation date" that sits six to eighteen months before the tax year begins. Cook County, Illinois uses a multi-year rolling analysis of sales ^[2]. Most other places use a single snapshot date.

A good comp sold arms-length (not a foreclosure, estate sale, or family transfer), within roughly one mile of your property, within 12 months before the valuation date, and with similar square footage, lot size, age, and condition. "Similar" means within about 15 to 20 percent on size and age. Bring at least three. Five or six persuades boards more, because it shows a pattern instead of a lucky pick.

Here's what makes a comp actually useful at a hearing:

• The sale price per square foot is lower than your assessed value per square foot
• The comp genuinely matches your condition (not a gut-renovated home versus your 1970s original)
• You can document the differences (a newer kitchen adds value, and you can quantify the adjustment with local contractor or appraiser cost data)

Where to get comps: your county assessor's own website publishes recent sales in most jurisdictions. Zillow, Redfin, and Realtor.com show sold prices. Multiple Listing Service (MLS) data is more complete, but you need a real estate agent to pull it. New York keeps a public sales database through the Office of Real Property Tax Services ^[3].

One move first: look up your own property on the assessor's site. If they publish a comparable sales grid, that's the single most useful document you can bring. It shows exactly which homes they used and lets you attack their choices head-on.

How does an independent appraisal help, and is it worth the cost?

A licensed independent appraisal is the strongest evidence you can put in front of a board. Assessors take it seriously because a state-licensed appraiser has a license on the line and has to follow USPAP, the Uniform Standards of Professional Appraisal Practice ^[4]. An appraiser's opinion of value, dated close to the assessor's valuation date, is hard to wave away.

Cost runs roughly $300 to $600 for a standard single-family appraisal. In high-cost markets like San Francisco or New York City it can hit $800 to $1,200. That's real money. It's worth it when your tax savings over three to five years clearly beat the fee. Say your home is over-assessed by $50,000 and your tax rate is 1.5 percent. You're overpaying $750 a year. The appraisal pays for itself in under a year.

If the math doesn't work, a well-built comp analysis you prepare yourself does almost the same job at the informal level. Plenty of homeowners win the assessor's informal review with nothing more than a printed comp grid and photos. Save the formal appraisal for the formal hearing or the state board of equalization if the informal review fails.

One detail that trips people up: the appraisal must be retrospective. It should value the property as of the assessor's valuation date, not today. An appraisal dated today against a January 1, 2024 valuation date is weaker evidence, and boards will say so out loud.

What property record errors should you check before anything else?

Before you spend a dollar on comps or an appraisal, pull your property record card from the assessor's office. It's a public document, and in most counties you can download it from the assessor's website. It lists every data point behind your value: square footage, bedrooms, bathrooms, lot size, construction quality grade, and any outbuildings or additions.

Errors in this record are the easiest wins in property tax appeals. Common ones:

• Square footage listed higher than reality (measure your living area yourself; garages and unfinished basements usually don't count)
• Bathrooms that don't exist
• A basement coded as finished when it isn't
• A garage still on the record after it was torn down
• A construction quality grade set too high for the actual condition

Find an error and you may skip the hearing entirely. Most assessors run an informal correction process. Bring a tape measure, photos, and your property record card. This category wins at the highest rate because the assessor simply made a factual mistake, and correcting facts isn't a judgment call.

For a walkthrough of what a property record card looks like and which fields to check, the Cook County Assessor has a public record system that lays out each data field.

Does property condition evidence really move the needle?

Yes, but only if you document it right. "Condition" in tax terms means physical defects that cut market value, not normal wear. What counts:

• Foundation cracks or settling (get a structural engineer's written report)
• Roof damage (a contractor's written replacement estimate)
• Outdated systems like knob-and-tube wiring or galvanized plumbing that limit financing (an inspector's report)
• Flood or water damage (photos plus remediation invoices)
• Environmental problems like an underground storage tank (an environmental assessment)

What generally doesn't count: old carpet, a kitchen frozen in 1995, a floor plan you don't like. Those are cosmetic preferences, and assessors ignore them unless you put a dollar figure on them.

The right way to present condition evidence is to pair it with a dollar estimate of the hit to market value. A contractor's estimate showing $40,000 in roof and foundation work beats a stack of photos. If you have a home inspection report, bring it. A licensed inspector's written report carries more weight than your own account of the problems.

One more thing worth knowing. Your assessor may have never seen your home. Many jurisdictions run mass appraisal models that set values algorithmically, with nobody walking inside. The IAAO standard for mass appraisal allows a coefficient of dispersion up to 15 percent for residential property ^[5]. Values that land 15 percent off sit inside their own acceptable range. Condition evidence is how you pull your home out of that statistical average.

What does the assessor's evidence look like, and how do you counter it?

At a formal hearing the assessor usually brings three things: your property record card, a comparable sales or cost-approach worksheet, and sometimes a mass appraisal model printout. Their evidence often has soft spots you can push on.

Common assessor weaknesses:

• Their comps include sales with different condition or location that pull the value up
• They leaned on a cost approach (replacement cost minus depreciation) while ignoring that buyers in your area don't pay replacement cost
• Their data is stale and predates a market downturn
• They bumped your quality grade off an exterior-only look and missed interior problems

Ask for the assessor's evidence packet before the hearing. Most states require them to share it in advance. Texas Tax Code Section 41.67 requires the appraisal district to hand over the information it plans to use no later than 14 days before the hearing ^[6]. Show up without their evidence and you're fighting blind.

Once you have their comps, run each one through the same test you used for yours: price per square foot, condition, location. If their "comparable" is a renovated home on a cul-de-sac and yours is a 1960s original on a busy road, write that down and say it plainly.

How do you organize and present your evidence at the hearing?

Boards move fast. An informal hearing runs 10 to 15 minutes. A formal hearing might give you 30. Walk in with a packet that tells your story in the first 60 seconds.

A standard evidence packet has these sections, in this order:

1. Cover page: your name, property address, parcel ID, hearing date, and the value you're requesting 2. Your property record card with errors circled 3. Your comp grid (a simple table: address, sale date, sale price, square footage, price per square foot, and notes on differences from your home) 4. Photos of your property showing condition 5. Any contractor estimates, inspection reports, or the appraisal 6. A one-page summary: "The assessed value is $X. My comps show market value is $Y. I'm requesting a reduction to $Y."

Bring enough copies for the room. Boards usually seat two to five members. Bring five to be safe, and keep one for yourself.

Speak in numbers, not feelings. "The assessor valued my home at $185 per square foot. My five comps average $157 per square foot. That's a $28 per square foot overvaluation on 1,800 square feet, or $50,400." That statement gets reductions. "I think it's too high" gets a polite nod and nothing else.

Want a structured way to build this packet? The TaxFightBack DIY appeal kit walks through each section with fillable templates so you're not starting from a blank page.

What's the difference between market value evidence and unequal appraisal evidence?

Some states hand you two separate grounds for appeal. The first is market value: your home is assessed above what it would sell for. The second is unequal appraisal: your home is assessed at a higher share of market value than comparable properties nearby, even if the raw number is accurate.

Texas is the clearest example. Under Texas Tax Code Section 41.43, you can appeal on either or both grounds ^[6]. The unequal appraisal argument goes: "Even if $300,000 is fair market value, my neighbors with similar homes are assessed at $250,000, so I'm carrying more than my share."

An unequal appraisal case needs different evidence. You pull the assessed values (not sale prices) of comparable properties from the public assessor database. You're comparing assessment records, not sales. Many homeowners find this easier to build, because sales data can run thin while assessment records are always there.

Not every state allows this argument. It's strong in Texas, available in some form in New York, and limited or unavailable in California under Prop 13 ^[1]. Read your state's statutes before you spend time on it.

In places like Montgomery County or Gwinnett County, knowing the local standard (market value versus uniformity) before you build your packet saves a lot of wasted work.

What evidence won't work and why you should skip it

Save yourself the trouble by knowing what boards routinely toss.

What doesn't work:

• What you paid for the house years ago. A 2015 purchase price says nothing about 2024 market value.
• What your neighbor told you his house sold for. Hearsay, unverified, ignored.
• Automated estimates from Zillow and similar tools. They carry documented error. A CoreLogic analysis of automated valuation models found median absolute percent error running roughly 1.9 to 6.8 percent nationally, and individual estimates swing much wider ^[7]. Boards know this and dismiss them.
• Photos of your nice landscaping to show you take care of the place. Maintenance isn't a valuation argument.
• Your mortgage statement or what you still owe. Debt has no link to market value.
• Speeches about how unfair the tax system is. Possibly true. Useless at a hearing.

The mistake I see most is homeowners printing a Zillow estimate and presenting it as evidence. It almost never lands. Use recorded sales from the assessor's own database or the MLS instead.

In high-stakes jurisdictions like Los Angeles County or NYC, where assessments run into the millions, getting the evidence right the first time matters even more. Hearing slots are limited, and appeals can drag on for years.

How do deadlines affect what evidence you can use?

The appeal deadline usually falls 30 to 90 days after your assessment notice lands, and it varies a lot by state. Miss it and you wait a year. Miss it twice and you've handed over thousands in extra taxes you'll never get back.

Deadlines also shape your evidence:

• Comps have to come from the window the assessor used. Sales after the valuation date generally aren't admissible, though some boards allow them as background.
• An independent appraisal should be backdated to the valuation date. An appraiser can do this. Just ask for a "retrospective appraisal as of [valuation date]."
• Some states make you submit evidence before the hearing rather than bring it the day of. Texas requires the appraisal district to share its evidence 14 days out, and some boards impose reciprocal rules on you ^[6].

The IAAO tracks appeal procedures across jurisdictions ^[5], but always check your specific county's rules, because local practice sometimes drifts from the state statute.

In tight-window places like Bexar County in Texas, where the notice-to-deadline stretch runs about 30 days, having your evidence ready before the notice even arrives is the smart play.

What's a realistic success rate, and what reduction should you expect?

Nobody has perfectly clean national data on this. The steadiest source is the Lincoln Institute of Land Policy, which has studied appeal outcomes across major jurisdictions. Its research found that roughly 20 to 40 percent of formal appeals end in a reduction, with the rate swinging hard by county and by whether the appellant showed up with real evidence ^[8].

Some high-appeal counties look starker. Cook County, Illinois processes hundreds of thousands of appeals in a reassessment year, and residential appeals often produce some reduction when the homeowner brings evidence ^[2]. In Texas, where the system is built for access, the Comptroller reported that property owners who filed formal protests got reductions in about 59 percent of cases in 2022 ^[9].

Reduction sizes vary. Most residential winners see 5 to 15 percent knocked off assessed value. A $400,000 assessment cut to $350,000 saves $500 to $750 a year at a 1 to 1.5 percent tax rate. Stretch that across five years before the next reassessment and you've kept $2,500 to $3,750.

The honest caveat: preparation drives the numbers. That 20 to 40 percent average includes everyone who walked in cold. Homeowners with clean comp grids and documented errors win at much higher rates. I can't hand you a precise figure, because nobody tracks preparation quality, but the gap is real and it's large.

Do you need a lawyer or an appraiser, or can you really do this yourself?

For a standard residential appeal at the informal or county board level, you genuinely don't need a lawyer. Most states design the informal process to work for homeowners without counsel. The forms are simple, the hearings are short, and the evidence standards sit well below a courtroom.

Where a professional earns the fee:

• Commercial properties over $1 million in assessed value (the numbers justify the cost and the legal arguments get complicated)
• State-level appeals at a tax court or board of equalization, especially when the assessor fights hard
• Cases using special valuation methods like the income approach on rentals

Where you can handle it yourself with good evidence:

• Single-family homes under $1 million in most counties
• Cases with clear factual errors in the property record
• Cases with clean comparable sales showing over-assessment

A contingency firm (the "no savings, no fee" kind) typically takes 30 to 50 percent of your first-year savings ^[11]. Save $800 and they keep $240 to $400. That's a fair trade for people who don't want to spend the time. But spend four hours pulling comps and building a packet and you keep the full $800. The TaxFightBack appeal kit exists for homeowners who'd rather keep that money.

For counties with their own quirks, like Santa Clara County and its Prop 13 base year rules, spend 30 minutes reading the county's own appeal instructions before you decide whether to hire help.

Frequently asked questions

How many comps do I need for a property tax appeal?

Most boards want at least three comparable sales. Five or six is better because it shows a pattern rather than cherry-picking. Each comp should be an arms-length sale within roughly one mile and 12 months of your assessor's valuation date, with similar size, age, and condition. More comps give you room to lose one on a technicality and still support your argument.

Where do I find comparable sales for free?

Start with your county assessor's own website. Most publish recent sales records. Redfin and Realtor.com show sold prices for most US markets. The New York State Office of Real Property Tax Services maintains a public sales database. Your county clerk's deed records are also public. Avoid relying solely on Zillow estimates; use actual recorded sale prices.

Do I need a licensed appraisal to win an appeal?

No. A licensed appraisal is the strongest evidence but it isn't required at most informal hearings or county board hearings. Many homeowners win with a self-prepared comparable sales grid and photos. An appraisal becomes worth the cost ($300 to $600 typically) when your potential savings over several years clearly exceed the fee or when you're heading to a formal hearing at a higher board.

Can I use Zillow as evidence in a property tax appeal?

Boards routinely dismiss Zillow estimates as unreliable. Automated valuation models carry documented error rates and aren't based on a property-specific inspection. Use actual recorded sale prices from the assessor's database, deed records, or MLS instead. A Zillow printout might help you spot which homes to research, but the sale record itself is what you bring to the hearing.

What is unequal appraisal and how is it different from a market value appeal?

A market value appeal says your assessment is above what your home would sell for. An unequal appraisal appeal says your assessment is higher as a percentage of market value than comparable nearby properties, even if the absolute value is defensible. Texas explicitly allows both grounds under Tax Code Section 41.43. For unequal appraisal, you compare assessed values of similar homes, not sale prices.

What errors in my property record card are worth appealing?

Common winning errors include inflated square footage, bathrooms that don't exist, a basement coded as finished when it's unfinished, a garage still listed after it was demolished, or a construction quality grade set too high. Pull your property record card from the assessor's website and measure your actual living space. These factual errors are often correctable without a formal hearing.

What photos should I take to support my appeal?

Photograph anything that shows physical problems reducing value: foundation cracks, water damage, roof condition, outdated electrical panels, unfinished spaces coded as finished, and the street setting if it differs from the assessor's comps. Date your photos. Pair them with written contractor estimates or inspection reports. Photos alone rarely move the needle; photos plus dollar estimates do.

Can I appeal if my home recently sold?

Yes, but your sale price cuts both ways. It works against you if you paid more than the assessed value, and for you if you paid less. In many states, a recent arms-length sale is treated as the best evidence of market value. If you bought the home below the current assessment, your closing disclosure is one of the strongest documents you can bring.

How far in advance do I need to prepare my evidence?

Some states require you to submit evidence to the board before the hearing rather than bring it the day of. Texas requires the appraisal district to share its evidence 14 days before the hearing, and some boards impose reciprocal rules. At minimum, have your packet ready at least a week out so you can organize copies and review it calmly. Last-minute prep tends to produce sloppy evidence.

Does a home inspection report help at an appeal?

Yes. A licensed home inspector's written report is useful condition evidence because it comes from a credentialed third party and documents defects you might otherwise just describe out loud. Pair the report with contractor cost estimates to turn the defects into dollar impacts. A report listing $25,000 in deferred maintenance is far more persuasive than the same report without cost context.

What happens if I lose at the county board level?

Most states let you appeal further to a state-level body, usually a board of equalization or state tax court. The evidence standards tighten and the process turns more formal, often requiring written filings and sometimes in-person hearings with the assessor's legal counsel present. At that level a licensed appraisal, and possibly an attorney, become worth considering, especially for high-value properties.

How do I calculate how much I could save if I win?

Subtract your target assessed value from your current assessed value. Multiply the difference by your effective tax rate (total tax bill divided by current assessed value). That's your annual savings. Then multiply by the years until your next reassessment, typically two to five. The total shows whether the appeal is worth your time and any evidence costs.

Sources

1. California State Board of Equalization, Proposition 13 overview: California uses purchase price as the base assessed value under Proposition 13, with annual increases capped at 2 percent
2. Cook County Assessor's Office, assessment methodology and appeals: Cook County uses a multi-year rolling sales analysis for mass appraisal and processes hundreds of thousands of appeals per reassessment cycle
3. New York State Office of Real Property Tax Services, public sales data: New York State maintains publicly accessible real property sales databases through the Office of Real Property Tax Services
4. Appraisal Foundation, Uniform Standards of Professional Appraisal Practice (USPAP): Licensed appraisers must follow USPAP when preparing appraisals, including retrospective valuations used as appeal evidence
5. International Association of Assessing Officers (IAAO), Standard on Mass Appraisal of Real Property: IAAO standard for residential property allows a coefficient of dispersion up to 15 percent, meaning assessments within that range are considered acceptable under mass appraisal norms
6. Texas Comptroller of Public Accounts, Property Tax Code Section 41.43 and 41.67: Texas Tax Code Section 41.43 allows appeals on both market value and unequal appraisal grounds; Section 41.67 requires the appraisal district to provide evidence at least 14 days before the hearing
7. CoreLogic, Automated Valuation Model performance studies: CoreLogic research found median absolute percent error for automated valuations ranged from approximately 1.9 to 6.8 percent nationally, with individual estimates varying much more widely
8. Lincoln Institute of Land Policy, property tax appeal research: Lincoln Institute research found roughly 20 to 40 percent of formal property tax appeals result in a reduction, with rates varying substantially by county and whether the appellant presented real evidence
9. Texas Comptroller of Public Accounts, 2022 Property Value Study and protest outcomes: The Texas Comptroller found that property owners who filed formal protests received reductions in approximately 59 percent of cases in 2022
10. Illinois General Assembly, Property Tax Code (35 ILCS 200): Illinois statutory framework for property assessments and board of review appeals procedures for residential property owners
11. National Taxpayers Union Foundation, property tax appeal guide: Analysis of contingency fee structures showing firms typically take 30 to 50 percent of first-year tax savings from successful appeals