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

Last updated 2026-07-09

What is the minimum number of comps for a property tax appeal?

Three is the floor. Most county assessment appeal boards, from Cook County in Illinois to Gwinnett County in Georgia, expect at least three comparable sales when you argue that your assessed value is too high ^[1]. Some boards say nothing explicit in their rules. That means the standard gets set by what actually wins, and practitioners across the country report that three well-chosen comps produce stronger decisions than one or two marginal ones.

Five is the sweet spot for most residential appeals. Five comps give you enough breadth to show a pattern without burying a volunteer board member who has 40 cases on the docket that afternoon. If your neighborhood has thin sales activity, three is fine. If you have eight genuinely close comps, use them all.

The number matters less than the quality. A single comp that is nearly identical to your home in square footage, age, condition, and location, and sold three months ago for less than your assessed value, does more work than five distant sales from different school districts and lot sizes. Quality over quantity is the actual math experienced appraisers use, not a slogan.

What makes a comp actually count?

Assessors and boards use four criteria, pulled straight from standard appraisal practice under the Uniform Standards of Professional Appraisal Practice (USPAP) ^[2]. A comp has to be:

1. Physically similar (square footage within roughly 15 to 20%, same number of bedrooms, similar lot size and construction type) 2. Locationally similar (within your neighborhood, ideally within one mile, definitely within the same school district) 3. Temporally similar (sold within 12 months of the assessor's valuation date, though 6 months is better) 4. Arm's-length (a normal market sale between an unrelated buyer and seller, not a foreclosure, estate sale, or related-party transfer)

Condition is the hard one. If your comp has a fully renovated kitchen and baths and yours is original 1985 everything, the board will discount that comp, or the assessor's rep will hammer you on it. You need comps in comparable condition, or you apply an explicit adjustment and explain it.

Fail any of these four tests and the sale is out. One bad comp invites the assessor to attack your whole grid instead of engaging with the ones that work.

Does more comps always mean a stronger appeal?

No. And this is where DIY appellants trip.

Submit ten comps and let three of them support the assessed value or higher, and you have just handed the assessor's rep ammunition. Boards take an average, or pick the middle of the range, or simply note that your own evidence contradicts itself. Every comp you include is evidence you own, and you answer for all of it.

The right approach: search broadly first. Pull every sale in your area from the past 12 months. Then filter hard. Keep only the ones that genuinely point to a value below your assessment. If five survive that filter, use five. If only three do, use three. Do not pad.

There is one exception. If your appeal goes to a formal hearing with an appraiser on the other side, more comps help you show a consistent pattern. At that level, seven to ten comps is reasonable and signals real work. For a standard informal review or an online portal appeal, three to five is right.

Where do you actually find comps for a property tax appeal?

You have four main sources, each with tradeoffs.

Your county assessor's property search portal. Free, and it covers every sale recorded in the county. Most portals let you search by address, subdivision, or parcel number and filter by sale date and property type. The data comes straight from deed recordings, so it is the same data the assessor used. La County, Cook County, and Montgomery County all keep publicly searchable sales databases online ^[3].

Zillow, Redfin, or Realtor.com recent sales. Filter by "sold" in the past 12 months, your ZIP code, and a square footage range. These sites often read easier than county portals. The downside: they sometimes miss off-market sales, and their condition data is spotty. Use them to spot candidates, then verify each sale against your county recorder's database.

Your county recorder or clerk of courts. Every deed is a public record. Many counties now post recorded deeds online for free. This is the definitive source for sale price and date.

A real estate agent's MLS pull. Agents can run a formal comp search (called a Comparative Market Analysis, or CMA) at no charge in most markets. This is one of the most underused free resources for DIY appellants. MLS data includes interior square footage, bedroom count, condition notes, and days on market, which makes filtering for genuinely similar properties much faster. Ask the agent for "sold comparables for appeal purposes" so they know what you need.

Skip Zestimate and AVM (automated valuation model) outputs as your comps. A Zestimate is not a comp. It is a statistical guess. Boards want actual closed sales with recorded prices.

How close does a comp have to be in distance and size?

Distance: within one mile for urban and suburban properties. Rural properties are the exception. There you sometimes stretch to three to five miles because sales are sparse, and boards generally accept that with an explanation.

Square footage: within 15 to 20 percent is the appraiser's rule of thumb. If your home is 1,800 square feet, you want comps in the 1,500 to 2,100 range. You can go a little outside that if the comp is otherwise nearly identical and you apply an explicit size adjustment.

Lot size: for single-family detached homes, try to stay within 25 percent of your lot size. For condos, lot size does not matter. For properties with acreage, lot value becomes its own sub-analysis.

Year built: within about 10 years is a reasonable target, though a full renovation can reset a property's functional age. A 1965 home gutted to the studs in 2018 is more comparable to other 2018-condition homes than to other 1965 originals.

Criteria	Ideal range	Acceptable stretch
Distance	Under 1 mile	1 to 3 miles (explain why)
Square footage	Within 15%	Within 25% (add adjustment)
Sale date	Within 6 months	Within 12 months
Year built	Within 10 years	Within 20 years (note renovations)
Lot size	Within 25%	Within 50% (single-family)

Stretch beyond these ranges on more than one dimension for any single comp, and cut that comp from your grid.

What time period do comps have to fall within?

The answer hangs on your state's assessment date, not today's calendar date ^[4].

Every state sets a statutory "lien date" or "assessment date," the date on which value is legally fixed. In California it is January 1. In Illinois it varies by township but is generally January 1 of the assessment year. In Texas, appraisal districts value property as of January 1 of each year ^[5]. You need comps that sold close to that date, ideally within 6 months before or after.

Here is where people go wrong. They appeal in September and use comps that sold in July and August. If the assessment date was January 1, those August sales are further from the valuation date than sales from the previous November. Anchor your comps to the assessment date, not the filing date.

If the market moved a lot between the assessment date and your hearing, you can argue time adjustments. That takes market data to support the adjustment rate, which is a more advanced move. For most residential appeals, comps within 12 months of the assessment date are enough and far simpler.

Some states reassess every 2 or 3 years. In those, boards will sometimes accept comps up to 24 months from the assessment date. Check your state's appeal board rules or the county assessor's office instructions.

How do you present comps on an appeal form?

Almost every county appeal form has a section called something like "comparable sales" or "evidence of market value." For each comp you typically fill in address, sale date, sale price, square footage, and price per square foot. Some forms also ask for the assessor's parcel number (APN) for each comp, which you look up in the assessor's database.

Format your comps in a grid. Put your subject property in the first row, then each comp below it. Calculate price per square foot for every entry. If your home's assessed value implies a price per square foot meaningfully higher than your comps, that gap is your argument.

Here is a bare-minimum comp grid:

Property	Sale/Assessment date	Sale price	Sq ft	$/sq ft
Subject (your home)	Jan 1, 2024 (assessment)	$420,000 assessed	1,850	$227 assessed
1234 Elm St	Nov 15, 2023	$365,000 sold	1,900	$192
789 Maple Ave	Feb 3, 2024	$358,000 sold	1,780	$201
456 Oak Ln	Dec 10, 2023	$372,000 sold	1,820	$204

The average price per square foot of these three comps is $199. Applied to your 1,850 square feet, that implies a market value of about $368,000, against a $420,000 assessment. That is your case.

Attach printouts or screenshots of each comp from the assessor's database or MLS. Add a Google Maps screenshot showing where each comp sits relative to your home. These visual aids take five minutes and make a real difference with boards that see hundreds of appeals.

Our Appeal Kit includes a pre-built comp grid spreadsheet that does this math automatically and formats everything to standard board requirements, so you are not designing tables from scratch.

Do I need to make adjustments to my comps?

For most informal residential appeals, no. Simple wins. If your raw unadjusted comps all sold below your assessed value, that tells a clean story, and you should not muddy it with adjustments you cannot defend.

Adjustments matter when your comps are not quite apples to apples. If every available comp has a finished basement and yours does not, you reduce the comp's value by the contributory value of that basement (usually estimated at cost per square foot of finished space, or by paired-sale analysis). If a comp is 300 square feet larger than your home, you subtract the value of that extra footage.

Appraiser-grade adjustments need data behind them. Saying "I subtracted $10,000 for the extra bedroom" with no source is weak. Saying "Based on paired sales in this neighborhood, an additional bedroom adds roughly $8,000 to $12,000 in value, per MLS data from the same period" is defensible.

If your appeal reaches a formal hearing with a staff appraiser on the other side, you will almost certainly face adjusted comps from the assessor. At that stage, matching them adjustment for adjustment counts. For an informal review or an online submission, clean unadjusted comps that all point lower are often all you need.

For complex appeals in large urban counties like Santa Clara or NYC, the assessor's office often has licensed appraisers reviewing evidence, so adjustment method matters more.

What if I can't find enough comps in my neighborhood?

Sparse sales are a real problem, especially in rural areas, niche property types, and neighborhoods where nothing turns over.

Your options, in order of preference:

Widen the search radius. Go from one mile to two or three, staying within the same general market area, school district, and property type. Tell the board plainly: "Sales within one mile were insufficient; these comps come from the broader market area with similar characteristics."

Go back further in time. If 12 months is not enough, try 18 or 24. Apply a time adjustment factor if the market moved, and document it with a market-wide price trend from a source like the Federal Housing Finance Agency's House Price Index ^[6].

Use the assessor's mass appraisal data against itself. Every assessor publishes a sales ratio study or a list of comparable properties they used to set your value. Request it through a public records request. Their own comps may support a lower value once you run the math.

Switch theories of value. If comparable sales are truly unavailable, boards in most states let you argue the income approach (for rentals) or the cost approach (what it would cost to rebuild, minus depreciation). The cost approach helps most with unique or older properties. This is more advanced ground, but it is a real option when the sales approach runs dry.

In counties with thin sales data, like some rural Georgia counties covered by Bibb County Tax Assessor or Gwinnett County Tax Assessor guidelines, the assessor's office sometimes publishes neighborhood factor tables you can use to cross-check your value.

How do comps work differently for condos vs. single-family homes?

Condos are easier in some ways. Units in the same building share identical construction, zero lot, and many features, so the best comp for a condo is another unit in the same building that sold recently. If a comparable unit two floors below yours sold for 15 percent less than what your assessment implies, that is a very strong comp.

What matters for condo comps: floor level (views and noise), unit condition, and specific interior finishes. Parking spaces and storage units can move value too.

Single-family homes take more nuance because no two houses are exactly alike. That is why adjustments matter more, and also why board members (who often own single-family homes themselves) have a gut sense of what makes a house more or less valuable.

For multi-unit and commercial properties, comparable sales still matter, but the income approach often carries more weight. If you are appealing a small rental in Hennepin County or an investment property in Los Angeles County, be ready to present both a rent roll and comparable sales.

What do assessors look at when they review your comps?

When you submit comps, the assessor (or their reviewer) asks four questions in roughly this order.

First: are these arm's-length sales? They flag any foreclosure, short sale, estate sale, or related-party deal and discard it. Include one without knowing, and it dents your credibility on the rest.

Second: are they actually comparable? They check whether your comps are materially smaller, older, or in a different condition tier than your subject property. If they are, the assessor notes it, either tossing the comp or applying their own upward adjustment.

Third: what does the price per square foot spread look like? Assessors are comfortable with this metric. Comps clustered tightly in a range that supports a lower value are much harder to dismiss than a single outlier.

Fourth: is there a trend that contradicts your comps? If the assessor can show neighborhood prices rose 12 percent between your comp's sale date and the assessment date, your comps need a time adjustment or the assessor applies one in their favor.

Knowing these four questions lets you pre-answer them. Note in your submission that all sales are arm's-length per the county's deed records. Note that you checked condition flags in the MLS. Note the sale dates relative to the assessment date. Anticipating the objections is half the fight.

Can I use Zillow or online home value estimates instead of real comps?

No. Not as a substitute.

A Zestimate, a Redfin Estimate, or any automated valuation model (AVM) output is not evidence of market value in a legal or quasi-legal proceeding. Appeal boards across the country reject these consistently. AVM accuracy swings widely by market and data density, and these tools are not equivalent to an appraisal or a comparable sales analysis ^[7].

Use these sites to spot which properties sold recently near you, then verify the actual sale price through your county recorder's records. That is the workflow: AVM tools as a search filter, county data as the evidence.

If you genuinely cannot find comps yourself and cannot get a CMA from an agent, a licensed residential appraisal costs roughly $300 to $500 in most markets. That appraisal is admissible evidence at almost any level of the appeal and carries real weight. For a home where the over-assessment costs you $1,000 or more a year in extra taxes, the appraisal pays for itself. For smaller savings, it is probably not worth it.

If you hire an appraiser, say you need an appraisal for assessment appeal purposes, with the effective date matching the assessor's valuation date. An appraisal dated today for a January 1 assessment value is less useful than one with the correct retrospective effective date.

Frequently asked questions

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

Three is the minimum most boards expect. Five is the practical sweet spot for residential appeals. More than five is worth doing only if all additional comps consistently support your position. Quality matters far more than quantity: one irrelevant or inconsistent comp in your grid can undercut the ones that work.

Can I use comps from a different neighborhood?

Only if you explain why. If your immediate neighborhood lacks recent sales, you can expand to a comparable nearby neighborhood and tell the board plainly that sales within one mile were insufficient. The further you go, the stronger your explanation needs to be. Boards will discount comps from areas with different school districts, access, or zoning without a clear rationale.

How old can a comp be for a property tax appeal?

Ideally within 6 months of your state's assessment date. Sales within 12 months of that date are generally accepted. Beyond 12 months, most boards want either a compelling explanation or a market-wide time adjustment supported by an index like the FHFA House Price Index. The key date is the statutory assessment date, not the date you file.

Do I need a licensed appraiser to present comps?

No, for most informal hearings and first-level reviews. Homeowners can present their own comparable sales evidence without professional credentials. A licensed appraisal becomes worth considering when the potential savings exceed $800 to $1,000 per year, when the appeal goes to a formal board hearing, or when the assessor's office has a licensed appraiser reviewing your submission.

Can a foreclosure sale count as a comp?

Generally no. Foreclosure, short sale, and distressed sales are not arm's-length transactions. Most state assessment statutes and USPAP guidelines exclude them from market value comparisons. If you submit one as a comp, expect the assessor to object immediately, and that objection will be valid. Check each sale's deed type in your county recorder's database before including it.

What if all my comps sold for more than my assessed value?

Then you do not have a case on market value grounds, at least not on comparable sales. Stop there. Either your assessment is actually fair, or you need a different theory of value, like a condition defect, an error in the assessor's property record (wrong square footage, wrong bedroom count), or an exemption you qualify for but have not claimed.

How do I get the sale price of nearby homes?

Your county assessor's property search portal and your county recorder of deeds are the best free sources. Recorded deeds are public records in every state. Zillow and Redfin also show recent sold prices, though verify each figure against the county record before using it. In non-disclosure states like Texas and Utah, sale prices may not appear in public records, so MLS data from an agent is your best option.

Should I include comps that sold for more than my assessed value?

No. Include only comps that support a value at or below your assessed value. Every comp you submit is evidence you own, and a board can average your entire submission. One high-priced comp can drag your implied value upward. Search broadly, then select only the comps that consistently support your argument.

How do I adjust comps that are not exactly like my house?

Appraisers adjust by feature: square footage at a price-per-foot rate, bedroom count, garage bays, condition. For informal appeals, explicit adjustments help only when your comps are moderately different. If you adjust, show your math and cite a source for your adjustment rates (like paired sales from your own market). Unexplained adjustments hurt more than they help.

What is a sales ratio study and how does it help my appeal?

A sales ratio study compares assessed values to actual sale prices across a jurisdiction. Many states publish these annually. If your county's ratio study shows assessments average 95 percent of market value but yours sits at 115 percent, that statistical evidence supports your appeal even without individual comps. Request your county's most recent ratio study from the assessor or the state revenue department.

Can I appeal without any comps at all?

Yes, if your appeal is based on a factual error in your property record. If the assessor lists your home as 2,400 square feet when it is actually 1,900, or shows four bathrooms when you have two, you can appeal on that error alone. Bring documentation (a floor plan, permit records, or a simple measurement). No comps needed when the assessment inputs are wrong.

Do comps matter differently at different levels of appeal?

Yes. At an informal review with an assessor's staff member, three clean comps presented simply often resolve the issue. At a formal board hearing, you may face a licensed appraiser with their own adjusted comp grid, and your evidence needs to match that rigor. If you go to tax court, comps become part of formal appraisal testimony. Calibrate your effort to the level of your hearing.

What is the difference between a comp and a CMA?

A Comparative Market Analysis (CMA) is a formatted report, usually prepared by a real estate agent, that organizes comparable sales with photos, maps, and feature comparisons. The underlying data is the same as what you would compile yourself. A CMA is not a licensed appraisal, but boards generally accept it as organized evidence. It is free from most agents and saves you significant formatting time.

How many comps do assessors use when they value my home?

Mass appraisal models used by most assessors are regression-based and draw on all sales in a neighborhood or market area, sometimes hundreds of transactions. Your assessor is not cherry-picking three comps; they are calibrating a statistical model. This is useful to know: you can request the sales data and model outputs under public records laws in most states, and sometimes the assessor's own data reveals an error in how your home was classified.

Sources

1. Cook County Assessor's Office, Appeal Instructions: County assessment appeal boards typically require at least three comparable sales as evidence of market value in residential appeals.
2. Appraisal Foundation, Uniform Standards of Professional Appraisal Practice (USPAP): USPAP Standards Rule 1-4 requires appraisers analyzing comparable sales to consider physical, locational, and temporal similarity, as well as arm's-length transaction status.
3. Los Angeles County Office of the Assessor, Property Search: Los Angeles County and other major counties maintain publicly searchable databases of recorded property sales used by both assessors and appellants.
4. International Association of Assessing Officers (IAAO), Standard on Mass Appraisal of Real Property: Assessment valuation dates (lien dates) vary by state and govern which comparable sales are most relevant to an appeal.
5. Texas Comptroller of Public Accounts, Property Tax Assistance Division: Texas Property Tax Code requires appraisal districts to value property as of January 1 of each tax year.
6. Federal Housing Finance Agency, House Price Index: The FHFA House Price Index provides market-wide price trend data usable to support time adjustments when comps predate the assessment date.
7. California State Board of Equalization, Assessment Appeals Manual: California's assessment lien date is January 1, and comparable sales should be anchored to that date for appeal purposes.
8. National Taxpayers Union Foundation, Property Tax Appeal Guide: Property tax appeal success rates are meaningfully higher when appellants present organized comparable sales evidence versus filing without documentation.
9. Montgomery County, MD Department of Finance, Property Tax Assessment Appeal: Montgomery County and similar large counties maintain online searchable sales databases that property owners can use to identify comparable sales for appeals.