How to pull your own comps from Zillow for a tax appeal

Last updated 2026-07-09

Why comps are the single most effective evidence in a tax appeal

Most assessors value residential property using a sales comparison approach. They find recently sold homes similar to yours, adjust for differences, and use those sales to justify their number. If their comps are wrong, weak, or cherry-picked, your job is to show better ones.

Comps win appeals because they speak the assessor's language. You are not arguing that your taxes feel high. You are showing that the market evidence does not support the assessed value. Hearing officers respond to that. Anecdotes do not close cases. A clean grid of five recent sales does.

The question is not whether to use comps. It is where to get them. A licensed appraiser pulls from the MLS through a service like Realist or CoreLogic, which costs real money. Zillow's sold data is free, public, and surprisingly complete for single-family homes in most metros. It will not match MLS depth in every county. But for a homeowner doing a solo appeal, it is good enough to build a credible case.

What is the assessor's valuation date and why does it control everything?

Your valuation date is the single date your assessor uses to estimate what your property is worth for tax purposes. Every state sets one by statute, sometimes called the lien date or assessment date. Your assessor estimates market value as of that specific day, not today and not last year ^[1].

If your valuation date is January 1, 2024, you need sales that closed before that date, usually within the six to twelve months leading up to it. A sale from eight months after the valuation date is weaker evidence, and some jurisdictions will not accept it at all.

Here are the valuation dates for the states homeowners ask about most:

State	Valuation Date	Source
California	January 1	Cal. Rev. & Tax. Code § 2192
Texas	January 1	Tex. Tax Code § 23.01
Illinois	January 1	35 ILCS 200/9-95
New York	Varies by municipality	NY RPTL § 301
Florida	January 1	Fla. Stat. § 192.042
Georgia	January 1	O.C.G.A. § 48-5-2
Minnesota	January 2	Minn. Stat. § 273.11
Missouri	January 1	Mo. Rev. Stat. § 137.115

Look up your state's exact date before you filter anything. Getting it wrong means your entire comp set can fall outside the acceptable window ^[2].

Once you have the date, your Zillow search window is roughly this: sold between 12 months before the valuation date and the valuation date itself. Some appeal boards extend the window to 18 months if the local market was thin. Check your jurisdiction's appeal rules.

How do you set up a Zillow search to find valid comparable sales?

Six filters turn a Zillow map into a comp set: Sold status, a date range that ends at your valuation date, a half-mile to one-mile radius, matching home type, square footage within 20 percent, and bedroom count within one. Set them in that order and you get usable sales in minutes.

Go to Zillow.com, enter your address, and let the map load. Open the Filters panel.

First, change the listing type to Sold. This hides active listings. Active list prices are asking prices, not sales. Assessors and hearing officers will not accept them, and neither should you.

Second, set the sale date range. Use the Date Sold filter to cap the window at your valuation date. Start 12 months before that date. Widen to 18 months only if sales are scarce.

Third, set a radius. Stay within roughly half a mile to one mile of your home in a dense suburb. In rural areas, expand to two or three miles. Proximity matters because assessors expect the same market area, not a zip code three towns over.

Fourth, match home type exactly. Single-family if your home is single-family, condo if it is a condo. Mixing types is a common mistake, and hearing officers catch it immediately.

Fifth, set square footage to plus or minus 20 percent of your home's finished square footage. If your home is 1,800 square feet, the range is 1,440 to 2,160. Some appraisal guidelines allow plus or minus 25 percent. Tighter is better for credibility.

Sixth, filter by bedrooms if the local housing stock is uniform. In many subdivisions, bedroom count tracks square footage and you can skip this. In neighborhoods with a wide mix, keep bedroom count within one of yours.

Do not apply price filters. You want the market to show you what homes sold for, not confirm a number you already picked. Filtering by price is the kind of thing that, if it surfaced at a hearing, would sink your credibility.

Which property details on a Zillow listing are reliable for comp work?

Trust the sale date, sale price, square footage, year built, lot size, and bed and bath counts. These come from county assessor records or MLS feeds and are right most of the time. Ignore the Zestimate, days on market, and any user-entered condition notes. Zillow pulls data from public records, MLS feeds where available, and user submissions, and those fields carry very different reliability ^[3].

The Zestimate is Zillow's automated estimate, not a sale price. Never use it as evidence. Days on market is often missing for older sold listings. Condition and renovation notes are frequently blank or self-reported.

For each comp, cross-reference the sale price and date against your county assessor's public records portal. Most counties now run searchable databases. If the county record matches Zillow, you have confirmation. If they differ, use the county record and note the discrepancy. Showing you verified against the primary source makes your evidence far harder to dismiss.

If your county's portal is hard to work with, see how other metro homeowners handle it. The Cook County tax assessor tax bill has a public property search that confirms sales, and the Gwinnett County tax assessor publishes deed transfers searchable by address.

How many comps do you actually need for a tax appeal?

Three is the practical minimum. Five is better. More than eight starts to look like you are fishing for outliers, and a sharp hearing officer will say so.

Volume is not the goal. A tight, credible set of sales is. You want a reasonable person to look at your grid and say: yes, those are similar homes, and yes, they sold for less than the assessed value on the subject property.

If you cannot find three sales within half a mile that support a lower value, widen your radius before you widen your date range. If you still cannot find three, that is real information. It may mean your assessment is defensible. It may mean your neighborhood had few sales and you need to work harder on adjustments.

One sale two blocks away from a nearly identical home, closed two months before the valuation date, beats six sales from a different subdivision a mile off. Quality wins.

How do you adjust comps for differences and present them in a grid?

Raw sale prices are not your argument. The adjusted value is. Adjustments account for the differences between each comp and your home, and this is exactly where most DIY filers get vague. Do it well and you stand out.

The standard residential adjustment categories are gross living area (price per square foot), lot size, year built, garage, basement (finished versus unfinished), pool, and condition. You do not need to be precise to the dollar. You need to be directionally honest and consistent.

A simple grid works. Here is a template:

Factor	Your Home	Comp 1	Comp 2	Comp 3
Sale Price	(subject)	$310,000	$295,000	$325,000
Sale Date	(valuation date)	8 mo. prior	5 mo. prior	11 mo. prior
Sq. Ft.	1,800	1,950	1,720	1,880
Year Built	1988	1991	1985	1990
Garage	2-car	2-car	1-car	2-car
Adjusted Value		$305,000	$298,000	$318,000
Indicated Value	$307,000 avg.

For square footage, use a price-per-square-foot figure pulled from the comps themselves. If Comp 1 sold for $310,000 at 1,950 square feet, that is about $159 per square foot. If your home has 130 fewer square feet than Comp 1, the downward adjustment to Comp 1 is roughly $20,670, making the adjusted sale about $289,000. Keep the arithmetic visible so a hearing officer can follow every step.

Do not make adjustments you cannot defend. If you are unsure how to value a garage, call the homes similar and leave the adjustment at zero, rather than guessing a number that invites a challenge.

The TaxFightBack DIY appeal kit includes a pre-built comp grid spreadsheet that runs these calculations for you, which saves time and cuts arithmetic errors if you want a structured starting point.

What if Zillow's sold data is thin or missing in your area?

Zillow's coverage runs weaker in rural counties, in non-disclosure states where sale prices are not public record, and in markets where sellers skip MLS syndication. The non-disclosure states include Alaska, Idaho, Kansas, Louisiana, Mississippi, Missouri, Montana, New Mexico, North Dakota, Texas, Utah, and Wyoming, though disclosure norms in Texas are shifting ^[4].

When Zillow leaves you short, work these backups in order:

1. Your county assessor's property search portal. Most now show recent sales with prices. The Montgomery County property tax and Bexar County tax assessor pages point to counties with detailed public search tools.

2. Redfin's sold search. Redfin pulls MLS data in many markets and often shows more sales, with better condition photos, than Zillow.

3. Your county recorder or register of deeds. Deed transfers are public record everywhere, and most counties post them online. The sale price may sit on the deed, or you may need to decode a transfer tax stamp (divide the transfer tax by your county's rate to get the price).

4. ATTOM Data or PropStream. These paid services run $99 to $200 per month and give you MLS-grade comp data. For one homeowner appealing one property, that is not worth it. For a landlord with several properties, it can pay off.

In non-disclosure states, your assessor is working from the same limited data you are. Say so at the hearing. If the assessor cannot show the sales they used to justify your value, ask them to produce their comparable sales report. You have that right in most jurisdictions.

How do you find out which comps your assessor actually used?

Ask. Most assessors will share their comparable sales when you request them. The formal route is a public records request, sometimes called a FOIA request at the federal level, though state open-records laws apply here. Request the comparable sales analysis or the field appraisal card for your property ^[5].

Many counties make it even easier. When you file an appeal or request an informal review, the assessor's office often sends a package that includes the comps they relied on. Read that package before you finalize your own set.

Why does this matter? If you show up with five comps that support a lower value and the assessor has five that support the assessed value, the hearing turns into a credibility contest. Win it by showing their comps are less similar to your home than yours are, or that they used sales from outside your neighborhood while ignoring closer ones. That is a strong argument.

The Lincoln Institute of Land Policy, in a 2021 study of assessment practices across major U.S. cities, found that "assessment ratios are often higher for lower-value properties than for higher-value properties within the same jurisdiction," which suggests the sales assessors use are not always drawn from the same market segment as the subject property ^[6]. Keep that in mind when you review their comps.

Can you use Zillow's Zestimate as evidence in a tax appeal?

No. Do not do this.

The Zestimate is an automated valuation model. Zillow itself says the Zestimate "is not an appraisal" and should not substitute for a professional valuation ^[7]. Assessors and hearing officers know this. Cite the Zestimate and you lose credibility on the spot, and the rest of your case gets read with more suspicion.

The Zestimate has one narrow use: a rough sanity check before you start. If Zillow's own model puts your home below the assessed value, the market data probably supports an appeal. But the number itself never goes into your evidence packet.

How do you document and present your Zillow comps at an appeal hearing?

Save a PDF of each Zillow listing for your comps. Include the full page showing the sold price, date, address, square footage, year built, and photos. Photos matter, because they help you argue condition.

Order your packet like this: a cover page with your parcel number, the appeal, and your requested value; your comp grid with the adjustment table; then each comp listing as a supporting exhibit, labeled Exhibit A, B, C, and so on.

Bring three copies to any in-person hearing. One for the hearing officer, one for the assessor's representative, one for you. If the hearing is virtual or by mail, confirm the submission format with the assessor's office ahead of time.

Keep it simple. You have maybe 10 to 15 minutes in most informal hearings. Lead with the grid. Say something like: "These five sales are the most similar homes to mine that sold closest to the valuation date. Adjusted for size and condition, they indicate a market value of $X, which is $Y below the assessed value." Then stop and let them respond.

For how formal hearings play out in specific metros, see how LA County property tax and Santa Clara property tax appeals are structured, since California runs one of the more formalized processes in the country.

What common mistakes will get your comps thrown out?

Five mistakes sink DIY comp sets: active listings, sales outside the date window, comps from the wrong market area, ignored condition differences, and a pile of sales with no grid. Each one gives the assessor an easy reason to dismiss your evidence.

Using active listings instead of sold properties. This comes up constantly. An active list price is an asking price, not a market transaction. Assessors will say so, and they are right.

Using sales outside your valuation date window. A 2022 sale, when your valuation date is January 1, 2021, may not be accepted. Check your jurisdiction's rules.

Picking comps from a different market area. Using a sale from a nicer subdivision a mile away to argue for a lower value is actually an argument that your home should be assessed higher. Keep your comps in the same neighborhood tier.

Ignoring condition differences. If your comp sold high because it was fully renovated and your home still has 1980s finishes, adjust the comp downward or note the difference explicitly. Pretending condition does not exist is easy to attack.

Submitting too many comps with no story. Seven comps with no adjustments and no grid looks like you printed whatever Zillow showed you. Three comps with clean adjustments looks like preparation.

For how different county assessors handle comp evidence, see the Bibb County tax assessor and Hennepin County property tax pages, which spell out what their offices want in a formal appeal submission.

Is Zillow good enough, or do you need a paid appraisal?

For most residential appeals seeking a modest reduction, Zillow-sourced comps in a clean grid are enough to win at the informal review or the first formal hearing. A paid appraisal makes sense in three situations: your potential tax savings are large, you are appealing to a state board of equalization where appraisal evidence carries more weight, or your market has thin Zillow data.

A licensed appraisal costs $300 to $600 for a standard single-family home ^[8].

The math is straightforward. Say your home is assessed at $500,000 and your effective tax rate is 1.2 percent. Every $50,000 reduction saves you $600 a year. A $400 appraisal pays off in under a year. Now say your home is assessed at $250,000 and you think it is worth $230,000. The annual savings at 1.2 percent is $240. A paid appraisal does not pencil out there.

DIY comps from Zillow, organized correctly, are free. That is the main reason to learn this yourself instead of hiring a contingency firm that takes 30 to 50 percent of your first-year savings ^[9].

The TaxFightBack DIY appeal kit walks through the whole evidence-building process step by step, worth a look if you want one structured guide rather than piecing together county-specific instructions.

Frequently asked questions

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

Yes, with documentation. Print the full Zillow listing page showing the address, sold price, date, and property details. Cross-reference the sale price against your county assessor's public records to confirm accuracy. Hearing officers treat Zillow listings as secondary evidence: useful and accepted, but stronger when verified against the county deed or assessor database.

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

Aim for sales within 12 months before your assessor's valuation date. Most state appeal boards accept sales up to 18 months prior if the market was thin. Sales after the valuation date are weaker, and some jurisdictions will not accept them at all. Your state's valuation date is set by statute; look it up before filtering Zillow.

How close to my home should comparable sales be?

Half a mile to one mile is the standard target in suburban markets. In dense urban areas, one to three blocks is better. In rural areas, two to three miles may be necessary. Proximity is a credibility signal: a sale from your own street carries more weight than one from a different neighborhood, even if the homes are similar on paper.

Does Zillow show all home sales, or does it miss some?

Zillow misses sales in non-disclosure states where sale prices are not public record, and it sometimes lags county records by weeks or months. It also has gaps in rural markets and for-sale-by-owner transactions that never hit the MLS. For those gaps, use your county assessor's online property search or your county recorder's deed records as a backup.

What is the difference between a Zestimate and a comparable sale for tax appeal purposes?

A Zestimate is an automated estimate Zillow generates from its own algorithm. It is not a market transaction and Zillow itself states it should not substitute for a professional valuation. A comparable sale is an actual arms-length transaction between a buyer and seller. Only actual sales are valid evidence in a tax appeal. Never cite the Zestimate in your hearing.

How do I adjust for differences between my home and the comps I find on Zillow?

Use a simple grid. Calculate a price-per-square-foot figure from each comp and apply it to size differences. Note differences in garage, basement, pool, and condition, and make directional adjustments. You do not need appraisal-level precision; you need to show your reasoning is consistent. A visible, honest adjustment table is far more credible than raw prices with no explanation.

What happens if the assessor's comps are different from mine?

That is normal. Your job at the hearing is to argue that your comps are more representative: closer to your home, more similar in size and condition, and sold closer to the valuation date. Request the assessor's comparable sales report before the hearing using a public records request. Review their selections critically for distance, similarity, and timing.

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

Three is the accepted minimum. Five gives you a more statistically defensible average. More than eight tends to look like cherry-picking. Focus on quality: a tight, consistent set of three or four sales that are genuinely similar to your home is more persuasive than a dozen loosely related ones.

Can I use Redfin or Realtor.com instead of Zillow for tax appeal comps?

Yes. Redfin in particular pulls directly from MLS feeds in many markets and often has better sold data than Zillow. Realtor.com is another option. The source matters less than the underlying data. Whatever portal you use, verify sale prices against your county's public records and document where each sale came from.

Do I need a licensed appraiser to appeal my property taxes?

Not at the informal review or first-level formal hearing in most states. A well-organized set of comparable sales you pulled and documented yourself is legally sufficient evidence in nearly all residential appeal processes. A licensed appraisal adds credibility and may be worth the $300 to $600 cost if your potential savings are large or if you are appealing to a state board.

What square footage filter should I use on Zillow when searching for comps?

Plus or minus 20 percent of your home's finished square footage is the standard starting point. For a 2,000 square foot home, that means filtering for 1,600 to 2,400 square feet. If you cannot find enough sales in that range, expand to 25 percent. Appraisal guidelines generally treat sales outside a 25 percent size range as less reliable comparable sales.

Can I use condo sales as comps for a single-family home appeal?

No. Condos and single-family homes trade in different market segments and are not comparable. Mixing types is a common mistake hearing officers catch quickly. Filter Zillow's home type selector to match your property type exactly. If you own a townhouse, use townhouse sales; if single-family, use single-family only.

What if I cannot find any comparable sales that support a lower value?

That is real information. It may mean the assessment is defensible given local market data. Before giving up, check whether you have an error in your property record instead: wrong square footage, incorrect bedroom count, a non-existent improvement. Property record errors are a separate and often easier grounds for appeal than market value arguments.

Sources

1. California State Board of Equalization, Property Tax Rules Rule 2: California's valuation date is January 1 each year under the sales comparison framework
2. Texas Comptroller of Public Accounts, Property Tax Assistance Division: Texas property valuation date is January 1 per Tex. Tax Code § 23.01
3. Zillow Research, Zestimate Methodology: Zillow sources sold data from public records and MLS feeds; field reliability varies by data type
4. National Association of Realtors, State Non-Disclosure Laws: Multiple states including Texas, Utah, and Wyoming do not require public disclosure of sale prices on deed transfers
5. U.S. Department of Justice, Freedom of Information Act Overview: Public records requests (FOIA and state equivalents) entitle citizens to government records including assessor comparable sales reports
6. Lincoln Institute of Land Policy, Diverging Fortunes: Why Property Tax Burdens Are Not Equally Shared (2021): The Lincoln Institute found that 'assessment ratios are often higher for lower-value properties than for higher-value properties within the same jurisdiction'
7. Zillow, Zestimate FAQ: Zillow states the Zestimate 'is not an appraisal' and should not substitute for a professional valuation
8. Appraisal Institute, Residential Appraisal Cost Overview: Licensed residential appraisals typically cost $300 to $600 for a standard single-family home
9. National Taxpayers Union Foundation, Property Tax Appeal Contingency Fee Survey: Contingency firms typically charge 30 to 50 percent of first-year tax savings as their fee
10. Illinois Compiled Statutes, 35 ILCS 200/9-95: Illinois sets January 1 as the assessment date for property valuation purposes
11. Florida Department of Revenue, Property Tax Oversight: Florida's valuation date is January 1 per Fla. Stat. § 192.042