How to look up comparable home sales for a property tax appeal

Last updated 2026-07-09

Why comparable sales are the core of any property tax appeal

Your county assessor values your home with a mass-appraisal model, and those models sometimes get it wrong. The strongest way to prove an over-assessment is to show what similar homes actually sold for around the time the assessor set your value. Comparable sales, called "comps" in appraisal practice, are the same evidence a real estate appraiser uses in a mortgage appraisal. Boards of equalization and assessment review boards expect them. Comps beat almost every other appeal argument.

Here's the practical reason. Say your home is assessed at $420,000 but three nearby homes of similar size sold for $370,000 in the same period. Now you have a documented gap the board has to address. Without comps, you're asking the board to take your word for it. Nobody does that.

The data you need is public record. You don't need a licensed appraiser, and you don't need to hand a contingency firm 25-40% of your savings. You need to know where to look and what to filter for.

What makes a sale "comparable" for property tax purposes?

An assessor or review board rejects a comp when it fails basic similarity standards. The rules aren't written in stone, but appraisal practice and most state assessment statutes point to the same four filters.

Sale date. The comp must sell close to your assessment date, which varies by state. Most states assess as of January 1. Uniform Standards of Professional Appraisal Practice (USPAP) guidance, which most state assessors follow, generally treats sales within 12 months as acceptable, with 6 months preferred ^[1]. Some states define this window in statute, so check yours.

Location. Closer is better. The standard is roughly 0.25 to 0.5 miles in dense suburban or urban areas. In rural markets, comparable sales might sit 2-5 miles away and still count, because so few homes sell. Your county appraisal district often publishes its neighborhood boundaries, which is the best proximity guide you'll find.

Physical similarity. Size (gross living area), age, bedroom and bathroom count, lot size, garage, and condition all matter. A workable range is within 10-20% of gross living area and within 10 years of age. You cannot compare a 2,100 sq ft home to a 4,000 sq ft home without heavy adjustment, and boards know it.

Arm's-length status. The sale must happen between unrelated parties with no duress. Foreclosure sales, estate sales between family members, and bank-owned REO sales are often excluded, though some jurisdictions allow them with adjustments. Check your state's definition. Texas, for example, defines a valid sale for appraisal purposes under Texas Tax Code Section 23.01 ^[2].

Filter	Rule of thumb	Why it matters
Sale date	Within 6-12 months of assessment date	Older sales reflect a different market
Distance	0.25-0.5 mi (urban), up to 2-5 mi (rural)	Location is the biggest value driver
Size	Within 10-20% of gross living area	Square footage drives price per sq ft
Age	Within 10 years of build year	Older homes depreciate differently
Sale type	Arm's-length only	Distressed sales skew low

Three to five comps is the standard expectation. One comp looks cherry-picked. Ten comps looks like you're burying a weak argument in volume.

Where can I find comparable home sales for free?

You have five reliable free sources. Each one has a tradeoff.

1. Your county assessor or appraisal district website. This is the best starting point. Most counties publish property search tools that show recent sales, assessment history, and property details. Search the sold properties around yours, filter by neighborhood, and save what you find. The assessor's own data carries weight in an appeal because you're using the source they used. Find your assessor's portal through the National Association of Counties directory ^[3].

2. Your state's deed recording portal. Real estate deeds get recorded at the county clerk or register of deeds, and most states have made these searchable online. The deed shows the sale price (or the documentary stamp tax, from which you back-calculate the price). This is raw, unfiltered sales data. States with free statewide portals include Florida (MyFloridaCounty.com), Illinois (iCash), and New York (ACRIS for NYC). In many states you go county by county.

3. Zillow's sold listings. Zillow keeps a national database of sold home prices. Use the map view, draw a search area around your property, filter to "Sold" within your date window, and copy the results. Zillow's data comes partly from MLS feeds and partly from public records, so it's broadly accurate but sometimes wrong on square footage or sale date ^[4].

4. Redfin. Redfin's sold data often runs more current than Zillow's because Redfin operates its own brokerage and has direct MLS access in markets where it works. Use the same map-filter approach. Redfin also shows days on market and price history, which helps you spot non-arm's-length sales.

5. FHFA House Price Index public data. The Federal Housing Finance Agency publishes quarterly house price indexes by metro area and state ^[5]. This won't hand you individual comp sales, but it tells you the rate of price change in your market. That's what you need to argue a sale from 8-10 months ago should be adjusted up or down to match your assessment date.

One note on Realtor.com and Trulia: both pull from data feeds similar to Zillow's. Use them to cross-check specific sales, but you probably don't need all three.

How do I use my county assessor's website to find comps?

Every county assessor site works a little differently, but the core workflow holds.

Start by searching your own property to confirm the data on file: square footage, bed/bath count, year built, assessed value. Screenshot and save it. If any detail is wrong (wrong square footage is more common than you'd think), that's a separate basis for appeal.

Then find the "sales search" or "recent sales" function. Some assessors have a map-based search. Others use a form where you enter a street name or subdivision. You want every sale in your neighborhood within the past 12 months. Download or copy the list.

Large counties with sophisticated portals, like Los Angeles County or Cook County, often let you pull a neighborhood comp report directly. These offices process hundreds of thousands of parcels and have built real public-facing tools. Smaller counties may give you only a basic parcel search.

Maricopa County in Arizona publishes a property search where you can filter sales by area code and date range, which makes pulling comps fast. Bexar County in Texas shows the comparable sales the district used in your own appraisal under the sales tab of your property record. That's a head start most homeowners don't realize they have.

Once you have a raw list, filter it with the criteria from the previous section. What's left is your working comp set.

How do I calculate price per square foot from comp sales?

Price per square foot (PPSF) is the most common appraisal metric and it's simple to run.

Take the sale price of the comp and divide it by its gross living area (GLA) in square feet. A home that sold for $350,000 with 1,750 sq ft of GLA sold at $200 per square foot. Do this for each comp. Then apply the median PPSF to your home's actual GLA to get an indicated market value.

Say your five comps produce PPSFs of $195, $202, $197, $208, and $199. The median is $199. If your home has 1,900 sq ft of GLA, the indicated value is $199 x 1,900 = $378,100. If you're assessed at $430,000, that's a $51,900 gap. That gap is the argument you bring to your hearing.

A few caveats. PPSF is a blunt tool. It doesn't adjust for lot size, basement finish, garage count, or condition. Professional appraisers make line-item adjustments for each difference, sometimes $5,000-$15,000 per feature depending on the market. You don't need that precision for most informal review hearings. But if your case goes to a formal board or state tax court, a licensed appraiser's opinion adds credibility. The Appraisal Institute's guidance puts a property tax appraisal for a standard single-family home in the $300-$600 range, though this varies by market and appraiser ^[6].

For a basic informal appeal, PPSF analysis is enough. The TaxFightBack DIY appeal kit walks you through a comp grid that matches the format most county boards actually use, so you're not guessing at presentation.

How far back can comp sales be for a property tax appeal?

This is state-specific, and it matters more than most homeowners realize.

Most states set an assessment date of January 1 of the tax year. Your 2025 tax bill was based on the value of your home as of January 1, 2025. In an appeal, you want sales that bracket that date: roughly July 1, 2024 through June 30, 2025, centered on January 1.

Some states write explicit look-back windows into statute. In California, Proposition 13 complicates this because reassessment only happens at change of ownership. When a reassessment does happen, Revenue and Taxation Code Section 110 defines market value as the price in an arm's-length transaction ^[7]. In Texas, the appraisal date is January 1 under Tax Code Section 23.01, and the district typically relies on sales from the prior calendar year ^[2].

If good comps are scarce inside the 6-month window, use older sales with a time-trend adjustment. This is where FHFA data earns its keep. If home prices in your metro rose 4% in the six months before your assessment date, a sale from eight months prior can be adjusted upward by roughly 4% to estimate what it would have sold for on your date. Boards accept this when you show your work.

Sales after the assessment date work in many states too, with time-trend adjustments applied in reverse. Check your state's assessment appeals statute to confirm what the board will take.

What if I can't find enough comparable sales near my home?

Thin markets are a real problem, especially in rural areas, custom-home neighborhoods, or any market where few homes turned over in the relevant period. Here's the play.

Expand your search radius in steps. Go from 0.5 miles to 1 mile, then to the full subdivision, then to the full assessor's neighborhood code. If the assessor groups your neighborhood with adjacent ones, those sales are fair game because the assessor used them too.

Expand your time window with adjustments. Pull sales from 12-18 months out and apply a market trend adjustment using FHFA data ^[5] or your local MLS market report.

Look for similar property types even when they're not identical. A 1,970 sq ft colonial can stand against a 2,050 sq ft ranch in the same neighborhood, with a note about the size and style difference.

Fewer comps demand more explanation. If you have only two usable comps, both should strongly support your value. A two-comp presentation where both sit below your assessment is a compelling argument if you acknowledge the thin data and explain why these are the most similar available sales.

Rural taxpayers hit this often. Madison County and Bibb County filers may need a 3-mile search radius to find anything usable. Document why you expanded the radius in your submission.

Can I use Zillow's Zestimate as a comp in my appeal?

No. A Zestimate is an automated valuation model estimate, not a sale price. No board of equalization will accept it as a comparable sale, and presenting it undercuts your credibility.

Zillow itself is clear about this. The company publishes its median Zestimate error rate (the median absolute percentage error) by geography. Per Zillow's own accuracy data, the nationwide median error for on-market homes runs around 2.4%, but for off-market homes it climbs to around 6.9%, and individual errors go much larger ^[4]. A Zestimate is a guess with a known margin of error. A recorded deed price is a fact.

What you can use from Zillow is its database of actual sold listings. When you filter to "Sold" and see a specific address, sale date, and sale price, that's a real transaction you can verify against deed records. Use Zillow to find sales. Use the county deed record or assessor database to confirm and document them.

One asterisk. If the assessor used an AVM to set your assessment and you can show their model overstated value against real sales, that's a valid argument. But you make it with real sales, not with a different AVM.

How do I document and present comp sales to the appeals board?

Format matters. Boards review hundreds of appeals and they recognize organized evidence on sight. A clean comp grid on two pages beats a stack of Zillow screenshots every time.

Build a simple table with these columns: address, sale date, sale price, gross living area (sq ft), year built, bed/bath count, lot size, price per sq ft, and one column for any notable differences from your property. Add a row at the bottom for your own home, using the assessed value in place of sale price.

Attach one page per comp with a printout of the assessor's record (showing the official sale data) or the deed recording. This proves you're not inventing numbers.

Include a short cover summary, one paragraph, that states your assessed value, the median indicated value from your comps, and the dollar and percentage gap. Boards like a clear bottom line.

Counties with formal evidence rules, like Gwinnett County or Cherokee County in Georgia (both use a Board of Equalization process with specific submission requirements), may require your evidence package a set number of days before the hearing. Miss that deadline and your comps can be excluded ^[8].

San Diego County appeals require evidence at least 5 business days before the hearing under California Revenue and Taxation Code Section 1606 ^[9]. Check your jurisdiction's rules before you finalize the package.

Are there any paid tools that are worth the money for comp research?

Mostly no, for a single-family homeowner running a DIY appeal.

The paid MLS access agents have is genuinely better data than Zillow or Redfin. It's more complete, updated faster, and includes fields the public portals hide (seller concessions, days on market, price reductions). But MLS access costs $30-$100 per month through a broker subscription or flat-fee MLS service, and most homeowners don't need it for one appeal.

CoreLogic and ICE (formerly Black Knight) sell professional comp tools to appraisers and lenders for hundreds of dollars per month. Not worth it for one appeal.

The one paid option that earns its cost in some cases is a limited appraisal report from a licensed appraiser, sometimes called a restricted appraisal report. These run $200-$400 and give you a defensible professional opinion without the full $500-$800 cost of a complete USPAP-compliant appraisal. If your assessment gap is large, say $50,000 or more in market value, the math favors paying for professional support.

For most homeowners with a $10,000-$40,000 gap, the free sources cover it. The Coweta County and Lake County assessors, like most, publish enough public data that a careful homeowner can build a credible three-to-five comp package without spending a dollar.

What common mistakes do homeowners make when pulling comps?

The list is short. The mistakes are expensive.

Using listing prices instead of sale prices. What someone asked for a home is irrelevant. What a buyer actually paid is the comp. Always use recorded sale prices.

Ignoring assessment dates. A 2023 sale doesn't help a 2025 assessment without a time-trend adjustment. Homeowners grab whatever recent sales they can find without checking whether those sales bracket the right date.

Cherry-picking without acknowledging outliers. If eight sales exist in your neighborhood and you present only the three lowest, the assessor's representative will present the other five. Present all the relevant sales and explain why certain ones are more similar to your home.

Using non-arm's-length sales. Foreclosures, short sales, and related-party transfers get challenged. Check the deed for red flags: a suspiciously round price (often an intra-family transfer) or language like "transfer on death" that signals no market transaction.

Presenting data without sources. Saying "similar homes sold for less" without documentation isn't evidence. Every number in your grid needs a verifiable source: a recorder's parcel number, an assessor record link, or a deed book and page reference.

The International Association of Assessing Officers publishes the mass-appraisal standards county assessors follow, including how comparable sales analysis is supposed to work ^[10]. Read it and you'll understand what the board is measuring your evidence against, which is exactly why the most common reason homeowners lose is that their evidence doesn't clear the board's evidentiary bar, not that their assessment was right.

Frequently asked questions

Where is the best place to find comparable home sales for a property tax appeal?

Start with your county assessor's website, which holds the same data the assessor used. Then cross-check with Redfin or Zillow's sold listings and your county deed recorder's portal. The assessor's own database is the most credible source in an appeal because you're using the official record. Large counties like Los Angeles and Cook County offer direct comp-search tools on the assessor site.

How many comparable sales do I need for a property tax appeal?

Three to five solid comps is the standard. One comp looks cherry-picked. More than six is fine if they all support your value, but ten comps with mixed results hurt more than help. Quality beats quantity: three comps that are genuinely similar in size, age, location, and condition are more persuasive than eight loosely similar ones.

How far back should comparable sales be for a property tax appeal?

Most states assess as of January 1. Aim for sales within 6-12 months of that date. Older sales (12-18 months) work with a time-trend adjustment based on your market's price change. Some states define the acceptable window in statute, so check your state's assessment appeals law. Texas uses the prior calendar year's sales; California uses the sale at transfer.

Can I use Zillow to find comparable sales for a property tax appeal?

Yes, but only for the actual recorded sale prices under Zillow's "Sold" filter, not the Zestimate. Zillow's Zestimate is an automated estimate with a median error around 6.9% for off-market homes, per Zillow's own accuracy data, and no appeals board accepts it as evidence. Use Zillow to find sales, then verify each one against your county's deed or assessor records before presenting it.

What does arm's-length sale mean and why does it matter for comps?

An arm's-length sale is a transaction between unrelated, uncoerced parties, each acting in their own interest. Foreclosures, short sales, estate sales to family members, and transfers between related businesses often fail this standard. Most state assessment statutes exclude non-arm's-length sales from comp use because the price doesn't reflect open-market value. Texas Tax Code Section 23.01 defines this explicitly.

How close does a comparable sale need to be to my home?

In dense suburban or urban markets, aim for 0.25 to 0.5 miles. In rural markets, 2-5 miles may be necessary because few homes sell in a given period. The best guide is your assessor's own neighborhood boundary map: if the assessor grouped those homes with yours for valuation, those sales are fair game. Expand your radius in steps and document why if you go beyond the immediate neighborhood.

What square footage difference is acceptable in a comparable sale?

A common rule of thumb is within 10-20% of gross living area. For a 2,000 sq ft home, that's roughly 1,600-2,400 sq ft. Larger gaps need adjustment. Boards generally accept comps outside this range if you acknowledge the size difference in your grid and either apply a per-square-foot adjustment or note that the PPSF still supports a value below your assessment.

Do I need a licensed appraiser to do a property tax appeal?

No, for most informal appeals. A well-organized comp grid built from public records works at the informal review and board of equalization level in most states. A licensed appraiser's opinion adds credibility if your case goes to state tax court or your assessment gap is large (over $50,000 in market value). A restricted appraisal report runs $200-$400 and is a middle-ground option worth considering.

Can I use recent home sales that are higher than my assessed value as evidence?

The assessor's representative certainly will if they exist. Present all the most similar sales you find, including the ones that don't favor you. If high sales exist but the lower ones are more genuinely comparable (closer in size, age, or condition), explain that in your submission. Showing only favorable comps and letting the other side produce the rest is worse than acknowledging them upfront.

What is price per square foot and how do I use it in a property tax appeal?

Price per square foot (PPSF) is the sale price divided by gross living area. Calculate it for each comp, find the median, then multiply by your home's actual square footage to get an indicated market value. If that figure sits below your assessed value, you have a quantified argument. PPSF is useful shorthand but doesn't adjust for lot size, condition, or features, so note any significant differences between your home and the comps.

Can I use sales that occurred after my assessment date as comps?

In many states, yes, with a time-trend adjustment applied in reverse. If homes appreciated 3% in the six months after your assessment date, a post-date sale should be adjusted down by 3% to estimate the value as of the assessment date. Some states' statutes specifically allow post-date sales. Check your state's assessment appeals law or ask the board directly whether they accept post-assessment-date evidence.

What format should I use to present comparable sales to a board of equalization?

A simple table: address, sale date, sale price, square footage, year built, bed/bath count, lot size, price per square foot, and a notes column for differences from your home. Add one page per comp with a printout of the assessor's or recorder's record as documentation. Lead with a one-paragraph summary showing your assessed value, the median comp-indicated value, and the dollar gap. Some counties require submission 5-10 days before the hearing.

Is the FHFA house price index useful for a property tax appeal?

Yes, as a supporting tool, not a primary comp source. The FHFA publishes quarterly house price indexes by metro area and state at fhfa.gov. Use it to calculate the time-trend adjustment when your best comps land 8-12 months before your assessment date, or to argue that rapidly changing prices make the assessor's value stale. It's a credible federal source that boards tend to accept.

What if my county's assessor website doesn't show comparable sales?

Go to the county recorder or register of deeds portal instead. Deed recordings are public record and most states have made them searchable online. You can also request a sales data report directly from the assessor's office under your state's open records or FOIA law. Failing that, Redfin and Zillow's sold filters are reliable fallbacks for most U.S. metro areas, though rural coverage can have gaps.

Sources

1. Appraisal Foundation, USPAP 2024-2025 Edition: USPAP guidance that most state assessors follow generally treats sales within 12 months as acceptable for appraisal comparables, with 6 months preferred
2. Texas Legislature, Texas Tax Code Section 23.01: Texas Tax Code Section 23.01 defines the January 1 appraisal date and arm's-length sale standard for property appraisal
3. National Association of Counties, County Directory: NACo directory helps homeowners find their county assessor's portal
4. Zillow Research, Zestimate Accuracy: Zillow's published accuracy data shows a median absolute percentage error of approximately 2.4% for on-market homes and 6.9% for off-market homes
5. Federal Housing Finance Agency, House Price Index: FHFA publishes quarterly house price indexes by metro area and state that can be used to calculate time-trend adjustments for comparable sales
6. Appraisal Institute: A property tax appraisal for a standard single-family home typically costs $300-$600 per Appraisal Institute guidance
7. California Legislative Information, Revenue and Taxation Code Section 110: California Revenue and Taxation Code Section 110 defines market value as the price in an arm's-length transaction for property assessment purposes
8. Georgia Department of Revenue, Property Tax Appeals: Georgia counties using a Board of Equalization process set specific evidence submission deadlines before the hearing
9. California State Board of Equalization, Assessment Appeals Manual: California Revenue and Taxation Code Section 1606 requires assessment appeal evidence to be submitted at least 5 business days before the hearing in San Diego and other California counties
10. International Association of Assessing Officers, Standard on Mass Appraisal of Real Property: IAAO standards guide mass-appraisal model methodology used by county assessors nationwide, including comparable sales analysis
11. Cook County Assessor's Office, Property Search: Cook County Assessor's website provides public-facing tools for searching recent comparable sales by neighborhood
12. Los Angeles County Office of the Assessor, Property Search: Los Angeles County Assessor's portal allows searches of comparable sales within neighborhoods