Using property tax records to build your own comp analysis

Last updated 2026-07-10

What information is actually in public property tax records?

Property tax records hold more than most homeowners expect. Every county in the United States keeps a public record for each parcel. That record typically lists the owner's name and mailing address, the legal description of the property, the land and improvement values broken out separately, the total assessed value, the tax bill amount, any exemptions applied, and the most recent sale price and date. Many counties also attach a property card with square footage, year built, number of bedrooms and bathrooms, construction type, and condition grade. That property card is where a lot of appeals are won.

The assessor's office uses these same records to mass-appraise your neighborhood every one to four years, depending on the state ^[1]. They build statistical models from sale prices and property characteristics. When you build your own comp analysis, you are reverse-engineering their model with the same underlying data. Your advantage is focus. You can zero in on your specific micro-neighborhood and find the handful of properties that most closely resemble yours, instead of relying on a county-wide average.

Sale prices in the tax record usually come from the deed filed at closing. Some states require full disclosure of sale prices on the deed, which makes this easy. Others, including Alaska, Idaho, Mississippi, Missouri, Montana, New Mexico, North Dakota, Texas, Utah, and Wyoming, do not require price disclosure, so sale amounts may show up as nominal (often $1 or $10) or missing entirely ^[2]. In non-disclosure states, cross-reference county records with a free tool like Zillow, Redfin, or your local MLS public portal to find recent sale prices.

Where do you find property tax records for free?

Start with your county assessor's or county auditor's website. Nearly every assessor now has an online parcel search, usually reachable from the county government homepage under "Assessor," "Appraisal District," or "Property Search." You can search by address, parcel number (also called APN or PIN), or owner name. If your county is large, a GIS map viewer may let you click parcels directly on a satellite image. That's the fastest way to gather neighboring properties.

Can't find the portal? Try the National Association of Counties (NACo) county finder at naco.org, or search "[your county name] assessor parcel search" in a browser. Regional appraisal districts in Texas (like the ones serving Bexar, Harris, or Dallas counties) run separate portals from the county tax collector, so you may need two sites ^[3]. For Cook County in Illinois, the Cook County Assessor tax bill portal has both assessed values and appeal history for every parcel.

State-level property record aggregators also exist. New York, California, and Florida all publish statewide parcel databases through their departments of revenue or taxation. Your state's open-records law (the FOIA or its equivalent) guarantees your right to this data even when it isn't posted online. A written request to the assessor's office must be answered within a set period, commonly 5-10 business days depending on state law ^[4].

Big counties with heavy-duty portals, like LA County property tax or Santa Clara property tax, even let you download bulk CSV extracts of every parcel in the county. That lets you run your own spreadsheet analysis across thousands of properties.

How do you choose the right comparable properties (comps)?

Picking comps is the step that decides your appeal, and it's where most DIY filers go wrong. Standard appraisal practice is to find properties that match in location, physical characteristics, and time of sale ^[5]. Here is how to think about each.

Location. Your comps should sit in the same neighborhood, subdivision, or at minimum the same school district zone. A half-mile radius is a reasonable start for suburban neighborhoods. In dense urban areas, limit it to the same block or the same building. Crossing a major road, a school boundary, or a zoning line can kill a comp, because those factors move market value on their own.

Physical characteristics. You want properties with similar gross living area (usually within 15-20%), the same number of stories, a similar lot size, similar age, and similar construction quality. The assessor's property card hands you all of this. If your house is 1,800 square feet and built in 1985, a 2,400-square-foot new build across the street is a weak comp no matter how close it is.

Time of sale. Assessors value property as of a specific "lien date" or "assessment date," which varies by state but is commonly January 1 of the tax year ^[6]. Sales used as comps should fall within 6-12 months of that date. A sale from three years ago, even for a perfect match, gets challenged because the market may have moved.

Aim for 5-10 comps. Three is the floor the assessor will take seriously. More than 12 starts to look like you cherry-picked, and it's just more work. If you can only find properties that are close but not perfect, that's fine. You'll adjust for the differences.

How do you make adjustments when your comps aren't identical?

No two properties match exactly, so real appraisers make dollar adjustments for the differences. You should too. It strengthens your argument, and assessors and review boards expect it.

The method is called the sales comparison approach. The rule is simple. If your comp has a feature yours lacks, subtract value from the comp's price. If yours has a feature the comp lacks, add value. Say your comp sold for $320,000 and has a finished basement your house doesn't, and finished basements in your area are worth roughly $20,000. You'd adjust the comp's effective sale price down to $300,000.

Where do you get adjustment amounts? A few practical sources:

• The assessor's own cost schedule. Most counties publish a "cost manual" or "schedule of values" that lists the per-square-foot contribution of garages, finished basements, decks, pools, and so on. This is the most credible source to use, because it's the same schedule the assessor used to build your assessment.
• Paired sales analysis. Find two sales of nearly identical homes where one has the feature and one doesn't. The price difference tells you the market value of that feature. This takes time, but it's very persuasive.
• Published adjustment guidelines. The Appraisal Institute publishes adjustment guidance in its textbooks, and some state boards of equalization publish their own guidance documents ^[7].

Keep your adjustments modest and grounded. An appeal board gets suspicious when adjustments run past 15-20% of the sale price in either direction. If your comps need that much adjusting, they probably aren't good comps.

For properties in large metros, the Gwinnett County Tax Assessor and Montgomery County property tax offices both publish their adjustment schedules online, which gives you a sense of what adjustments look like in practice.

What does a finished comp grid actually look like?

A comp grid is a table that lines up your property against each comparable sale so a reviewer sees the whole analysis at a glance. Here is a simplified example format using fictional numbers that show the structure:

Feature	Your Property	Comp 1	Comp 2	Comp 3
Address	100 Elm St	108 Elm St	212 Oak Ave	95 Elm St
Sale Date	n/a	03/15/2024	01/22/2024	05/10/2024
Sale Price	n/a	$285,000	$278,000	$295,000
GLA (sq ft)	1,650	1,710	1,580	1,720
GLA Adjustment		-$3,000	+$4,200	-$3,500
Garage	1-car	2-car	1-car	1-car
Garage Adjustment		-$8,000	$0	$0
Condition	Average	Average	Average	Good
Condition Adjustment		$0	$0	-$6,000
Adjusted Sale Price		$274,000	$282,200	$285,500
Indicated Value	$280,567

The "Indicated Value" is the average (or weighted average) of your adjusted comp prices. If your current assessed value is $310,000, this grid shows a roughly $30,000 over-assessment and becomes the centerpiece of your appeal evidence.

No special software required. A free Google Sheet or Excel file works fine. The goal is clarity: one page, easy to read, your property in the left column and comps lined up to the right.

How is assessed value different from market value, and why does it matter for comps?

This distinction trips up a lot of first-time filers. Market value (also called fair market value or FMV) is what a willing buyer would pay a willing seller with no unusual pressure. Assessed value is the number the county uses to calculate your tax bill, and it may be set at a fraction of market value depending on your state's "assessment ratio" or "assessment level" ^[6].

Say your state assesses at 80% of market value and your home's true market value is $400,000. The correct assessed value is $320,000. If the county has you at $370,000, the over-assessment isn't $370,000 against $400,000 market value. It's $370,000 against the $320,000 it should be at 80%.

This matters for your comp analysis because you have to compare apples to apples. You have two valid approaches:

1. Compare assessed values directly. Gather the assessed values of your comparable properties and show yours is higher on a per-square-foot basis. This sidesteps the assessment ratio entirely and is often the fastest argument. 2. Compare to sale prices, then apply the assessment ratio. Use your adjusted sale prices to establish market value, multiply by the local assessment ratio, and show that your assessed value exceeds that target.

Approach 1 is simpler and works well when the assessor has been inconsistent within your neighborhood. Approach 2 is more rigorous and is required in some states. Check your state's assessment ratio by searching "[state name] department of revenue assessment ratio" or looking at the state-by-state data published by the Lincoln Institute of Land Policy ^[8].

In Texas, where appraisal districts assess at 100% of market value by statute, you only need approach 2 ^[3]. In Maryland, the assessment level runs near 100% of market value but increases phase in over three years, which adds a wrinkle. The Montgomery County property tax guide explains the Maryland phased-in system in detail.

What mistakes kill a DIY comp analysis?

A handful of common errors sink otherwise solid appeals.

Using distressed sales. Foreclosures, short sales, estate sales, and sales between family members don't reflect open-market value. Assessors and appeal boards reject them as non-arm's-length transactions. Spot these by looking for sale prices far below the neighborhood median, or by checking the deed for language like "grantor and grantee are related" or "sold as-is."

Ignoring permits and unpermitted work. If your comp had a permitted addition that added 200 square feet after it sold, the assessor's record may not reflect it yet. Your comp's GLA could be understated, which makes the per-square-foot price look artificially high. Pull the permit history along with the tax record.

Cherry-picking in an obvious way. If there are 15 comparable sales in your neighborhood and you submit only the 3 lowest, the assessor will notice. Submit all relevant comps and argue honestly that even the full range supports a lower value. Boards trust homeowners who play it straight.

Confusing list price with sale price. Zillow shows both. Only the recorded sale price is evidence. List price is irrelevant and weakens your case if you cite it.

Failing to account for market direction. If the market rose sharply between your comps' sale dates and your assessment date, a plain average of older sales understates value and the assessor will say so. Use sales very close to the assessment date, or add a market trend adjustment.

One more thing: many homeowners over-document. Twenty pages of printouts saying the same thing in different ways is not more persuasive than a clean 5-page packet. The board member reading your file has 40 others to get through.

How do you get the property cards and internal assessor data for comps?

The property card (sometimes called a "field card" or "property record card") is the assessor's internal data sheet for a parcel. It lists the physical details the appraiser recorded during a field inspection: square footage, construction grade, room counts, condition rating, depreciation, outbuildings, and more. Get this for your own property and for your comps, because the square footage on Zillow can differ from what the assessor has on file, and the assessor's numbers are what your assessment is built on.

Most counties make property cards available one of three ways. Many are visible directly on the parcel search portal when you click into a property record. Others require a FOIA or open-records request, submitted in writing, which the county must answer within its statutory window (varies, commonly 5-10 business days for straightforward records) ^[4]. A small number of counties charge a nominal per-page fee, typically $0.10-$0.25 per page, though most states bar them from charging for the search itself.

When you pull your own property card, compare every field to reality. Assessors make data-entry errors. A garage recorded as finished that isn't, or 2,100 square feet recorded when the livable area is 1,875, can produce an inflated assessment that gets corrected the moment you point it out. That kind of error doesn't even need a board hearing. A phone call and a photo often fixes it.

For counties like Bexar County (San Antonio, TX) or Hennepin County (Minneapolis, MN), the portals are strong enough to pull full property cards online without any formal request.

How many comps do you need, and how recent do they have to be?

Five comparable sales is a solid floor for a residential appeal. The Uniform Standards of Professional Appraisal Practice (USPAP), the national standard appraisers follow, doesn't mandate a specific number. But in practice a single-family residential appraisal report (the 1004 form used for mortgage lending) has a minimum of three sales in the grid and typically uses five to eight ^[5]. Appeal boards have seen enough appraisals to know what a credible analysis looks like, so mirroring that format lends you credibility.

On recency: most state appeal rules require sales from within 12 months of the assessment date, and many boards prefer 6 months or fewer. The International Association of Assessing Officers (IAAO), the professional body for government assessors, recommends using sales from the 12 months ending on the assessment date as the primary pool and expanding to 24 months only when the market had insufficient activity ^[9]. State the time window you used and explain any exceptions.

Live in a low-turnover neighborhood where finding five sales within 12 months is genuinely impossible? Say so, explicitly, and explain the market conditions. A board will accept older comps if you show you pulled the full universe of sales. What they won't accept is an incomplete search dressed up as a complete one.

For very specific markets, like NYC property tax appeals through the Tax Commission process, or commercial appeals in LA County, the evidence standards run higher and you may need income-approach data alongside the sales comparison.

How do you turn your comp analysis into a formal appeal exhibit?

Most residential appeal processes accept a written submission with attachments, even when there is also a hearing. Your comp analysis becomes Exhibit A. Here is a format that works.

Page 1: Cover sheet. Your name, property address, parcel number, current assessed value, and the value you are requesting. Keep it to one paragraph.

Page 2: Your comp grid (the table from the earlier section). Label it clearly: "Exhibit A: Sales Comparison Analysis."

Pages 3 and on: One page per comparable. Include the parcel number, address, sale date, sale price, a screenshot or printout of the assessor's record for that parcel, and your adjustment notes. For each comp, note the source of the sale price (deed recorded with the county, or a specific MLS listing reference with date accessed).

Final page: A short narrative explaining your methodology. Two to three paragraphs: how you selected comps (radius, time frame, physical similarity criteria), how you determined adjustments, and your conclusion about market value.

Physically, either staple and tab the packet or use a simple binder with labeled dividers. Submitting electronically? A single PDF with bookmarks is ideal. Name the file with your parcel number and the word "appeal" so the clerk can find it.

If you'd rather start from a pre-built framework, the TaxFightBack DIY appeal kit has a comp grid template and a step-by-step evidence checklist you can work through in an afternoon. You keep every dollar of any reduction instead of handing a contingency firm 25-40% of the savings.

Once your packet is ready, check the deadline. Missing the filing window is the single most common reason legitimate appeals fail. Deadlines run from 30 days after your notice is mailed (many Midwest states) to as long as 90 days (parts of California and New York) ^[6]. Your assessment notice states the deadline explicitly.

What if the assessor's records have errors that inflate your assessment?

Data errors are more common than most people assume. A ProPublica and Chicago Tribune investigation of Cook County assessments found systematic overvaluation of lower-value homes, driven in part by outdated or incorrect property data ^[10]. That report focused on equity, but the mechanism it exposed, bad input data producing bad assessments, is universal.

Check these fields on your own property card and flag any that are wrong:

• Gross living area (GLA). Measure your home if you have any doubt. Assessors sometimes count unfinished areas, attics, or below-grade space that formal appraisal standards exclude from GLA.
• Bedroom and bathroom count. A half-bath counted as a full bath, or an unfinished bonus room counted as a bedroom, inflates your assessment.
• Year built and effective age. If the assessor has a newer effective age than the actual build date, the condition grade may be too high.
• Condition and quality grade. These are subjective, but if the assessor last visited your property years ago and conditions have declined (deferred maintenance, aging systems), the grade may no longer match reality.
• Lot size. Compare the assessor's lot acreage to your recorded survey.

For any error you find, the fastest fix is a phone call or informal review request to the assessor's office before you file a formal appeal. Many offices correct obvious data errors administratively without making you go through the full process. Get any correction in writing.

For Bibb County in Georgia or similar smaller counties, you can often speak directly with the field appraiser who valued your property, which makes resolving data errors quick.

How do you handle comps in a market that moved a lot recently?

This is the hardest scenario, and it cuts both ways. If the market dropped sharply between the assessment date and today, using sale prices from around the assessment date produces a value higher than current market, which hurts your appeal even if the assessment was accurate as of the lien date. If the market surged after a period of flat prices, old comps understate value and the assessor will point that out.

The professional fix is a time adjustment, also called a market conditions adjustment. You calculate the percentage change in median sale prices between two periods and apply it to your comp prices to bring them to the assessment date. The IAAO publishes guidance on calculating this, including paired sales analysis and repeat-sales methods ^[9].

For a DIY filer, a simpler move often works: use only comps that sold within 3-4 months of the assessment date. You may end up with fewer comps, but they're more defensible. With only 2-3 very recent sales, supplement with older sales and add a paragraph noting the market trend (flat, per the local MLS median data) to explain why the older sales still apply.

Appealing in a county where values moved dramatically? Say so in your narrative. "The market in this zip code rose approximately 8% between Q1 2023 and Q1 2024, per the county assessor's own published sales ratio study, and I have adjusted my comps accordingly." Using the assessor's own data against them is powerful.

Some states publish an annual sales ratio study that shows, by jurisdiction, how assessed values compare to sale prices. Minnesota's Department of Revenue, for example, publishes a statewide sales ratio study every year ^[11]. If your county's median ratio is above 1.0 (assessed values exceed sale prices), that study alone may support your appeal without individual comps.

Frequently asked questions

Can I use Zillow or Redfin data instead of official assessor records for my comps?

You can use Zillow and Redfin to find recent sales and estimate sale prices, especially in non-disclosure states where deed prices aren't public. But always verify the sale price and property details against the official assessor record before including a comp in your analysis. Appeal boards give more weight to county-recorded data than to third-party sites, which can carry stale or incorrect information.

How far back can sale dates go and still be used as comps?

Most state appeal rules and assessor offices expect sales within 12 months of the assessment date. The IAAO's standard is the 12 months ending on the valuation date as the primary pool, expanding to 24 months only when market activity is low. If you use sales older than 12 months, explain why (thin market, no closer sales available) and note whether prices held steady during the gap.

What is an assessment ratio and how do I find mine?

The assessment ratio is the percentage of market value at which the county is supposed to assess your property. It ranges from 10% in some jurisdictions to 100% in others. Your state's department of revenue or taxation publishes this, often in an annual sales ratio study. You can also find it on your property tax notice, which usually shows both assessed value and market value alongside the ratio.

Does a recent sale of my own home affect my assessment?

Yes, a lot. In most states, a recent arm's-length sale of your property is the strongest single indicator of market value, and the assessor can (and often will) use it to justify the current assessment. If your home sold recently above your old assessed value, expect an upward adjustment. If it sold below your current assessment, that sale price is your best evidence in an appeal.

How do I find the assessment ratio study for my state?

Search your state department of revenue's website for 'sales ratio study' or 'equalization study.' Minnesota, Wisconsin, Massachusetts, and Maryland all publish annual studies online. If your state doesn't publish one, try the state board of equalization or the state association of assessing officers. The Lincoln Institute of Land Policy also aggregates assessment ratio data across states in its Significant Features of the Property Tax database.

Can I use foreclosure sales as comps?

Generally no. Foreclosure sales, short sales, and REO (bank-owned) sales count as non-arm's-length transactions because the seller is under unusual pressure. Most state appeal statutes and assessor guidelines explicitly exclude distressed sales from the comp pool. Using them undercuts your credibility with the appeal board even if the numbers look favorable to you.

What if my neighborhood has very few recent sales?

When recent sales are scarce, you have two options: expand your search radius carefully (stay within the same school zone and zoning classification) or extend the time window to 18-24 months and add a market trend note explaining why older sales still apply. Be transparent about the thin market. You can also supplement with an income approach (for investment properties) or a cost approach for unique properties.

Do I need a licensed appraiser to build a comp analysis for a residential appeal?

No. For informal hearings and most formal residential appeals, a self-prepared comp analysis using public records is acceptable evidence. Some states require a licensed appraisal only for appeals above a certain value threshold (often $1 million or more) or for commercial property. Check your state's appeal statute. A licensed appraisal costs $300-$600 and is worth it when the potential tax savings are large.

How do I adjust for a finished basement or a pool?

The best source for adjustment amounts is your county assessor's own published cost schedule or schedule of values, which assigns dollar values to specific features. If that isn't published, use paired sales analysis: find two nearly identical sales where one has the feature and one doesn't, and use the price difference as your adjustment. Adjustments sourced from the assessor's own schedule are nearly impossible for them to dispute.

What if the assessor's records show wrong square footage for my home?

Measure your home's gross living area yourself, following the ANSI Z765 standard used by professional appraisers (finished, above-grade space only). If the assessor's record differs by more than a few percent, call the assessor's office first. Many will correct it administratively without a formal appeal. Bring your measurement notes and floor plan. If they won't correct it, include the error as a separate exhibit in your formal appeal.

Can I submit my comp analysis online or does it have to be in person?

It depends on your county. Many jurisdictions now accept electronic submissions through their appeal portal, by email, or through a document upload system. Others still require a physical packet mailed or hand-delivered to the assessor's office or appeal board. Your assessment notice or the county's appeal instructions will specify the accepted formats. When in doubt, both mail and email a copy and keep your delivery confirmation.

How long does a DIY comp-based appeal typically take?

The timeline varies by jurisdiction. Informal reviews (a conversation with the assessor before a formal hearing) can resolve in 2-6 weeks. Formal hearings before an assessment review board typically happen 30-90 days after you file. If you appeal to the state board or tax court, expect 6-18 months. Most residential appeals that get resolved with comp evidence finish at the informal or first-board stage within a few months.

What happens if my comps support a value higher than my current assessment?

Stop. Don't file an appeal if your honest comp analysis suggests your home is under-assessed. Filing draws the assessor's attention to your property. In some states and counties, a filed appeal lets the assessor increase your assessment during the proceedings. Run the numbers first. Only appeal if the analysis clearly supports a lower value.

Is there a difference in how I build comps for a condo versus a single-family home?

Yes. For condos, square footage and floor level matter more than lot size (which is typically shared). Comps should be in the same building or complex whenever possible, since different buildings have different amenity packages, HOA fee levels, and condition histories. If the same building had recent sales, those are your strongest evidence. Cross-building comps need adjustments for floor level, view, and unit condition.

Sources

1. International Association of Assessing Officers (IAAO), Standard on Mass Appraisal of Real Property: County assessors use mass appraisal models to value all properties on a regular reassessment cycle, typically every one to four years depending on the state.
2. National Association of Realtors, Non-Disclosure States reference: Alaska, Idaho, Mississippi, Missouri, Montana, New Mexico, North Dakota, Texas, Utah, and Wyoming do not require public disclosure of real estate sale prices on deeds.
3. Texas Tax Code, Section 23.01, Texas Legislature Online: Texas law requires appraisal districts to appraise property at 100 percent of market value as of January 1 of each year.
4. U.S. Department of Justice, Overview of the Freedom of Information Act: Federal and state open-records laws guarantee public access to government records, including property tax records; response deadlines are commonly 5-10 business days for straightforward requests.
5. Fannie Mae, Uniform Residential Appraisal Report (Form 1004) Guidelines: USPAP and standard residential appraisal practice require comparables to be similar in location, physical characteristics, and time of sale; the standard mortgage appraisal form uses a minimum of three comparable sales.
6. Lincoln Institute of Land Policy, Significant Features of the Property Tax: Assessment dates (lien dates) and assessment ratios vary by state; most states set the assessment date as January 1 of the tax year, and assessment ratios range from below 20% to 100% of market value.
7. Appraisal Institute, The Appraisal of Real Estate (14th Edition), Sales Comparison Approach: The Appraisal Institute's authoritative text describes paired sales analysis and cost schedule methods for deriving adjustment amounts in the sales comparison approach.
8. Lincoln Institute of Land Policy, Fifty-State Property Tax Comparison Study: The Lincoln Institute publishes an annual state-by-state comparison of property tax rates and assessment ratios across all 50 states.
9. International Association of Assessing Officers (IAAO), Standard on Ratio Studies: The IAAO recommends using sales from the 12 months ending on the valuation date as the primary pool for comparable sales, expanding to 24 months only when market activity is insufficient.
10. ProPublica and Chicago Tribune, The Tax Divide (investigation of Cook County assessments): A ProPublica and Chicago Tribune investigation found systematic over-assessment of lower-value Cook County homes, driven in part by outdated or incorrect property characteristic data in assessor records.
11. Minnesota Department of Revenue, Sales Ratio Study: Minnesota's Department of Revenue publishes an annual statewide sales ratio study showing by jurisdiction how assessed values compare to sale prices; a median ratio above 1.0 indicates assessed values exceed sale prices.
12. ANSI Z765-2021, Square Footage Method for Calculating: Measuring, Calculating, and Classifying the Square Footage of Detached and Attached Houses: The ANSI Z765 standard, referenced by professional appraisers and the Appraisal Institute, defines gross living area as finished, above-grade residential space only.