How to find off-market comparable sales for a property tax appeal

Last updated 2026-07-11

What counts as an off-market comparable sale in a property tax context?

An off-market sale is any arm's-length transaction recorded in the public deed record that never hit a multiple-listing service. Estate sales. Neighbor-to-neighbor deals. Foreclosure deeds-in-lieu. Builder sales to the first buyer. In a tax appeal, the phrase 'comparable sale' has a legal meaning that has nothing to do with real estate marketing. Most state statutes require assessors to value property at market value as of a specific lien date, and market value comes from all arm's-length sales, more than the pretty ones on Zillow.^[1]

That distinction changes everything. Say your assessor pulled five MLS-listed homes to justify your number, and four distressed or private sales nearby closed for less. Those quieter deals count as evidence just as much as the listed ones. In many jurisdictions, a sale is presumed arm's-length unless the assessor can prove a family relationship, an estate situation, or obvious duress. Produce a credible comp and the burden shifts.

The International Association of Assessing Officers (IAAO) defines an arm's-length sale as "one in which the buyer and seller are typically motivated, well-informed, and acting in their own best interests, without undue pressure or unusual terms."^[2] Meet that test and the sale belongs in your comp grid.

Why do off-market sales sometimes make stronger appeal evidence than MLS comps?

MLS comps have a survivorship problem. Only homes that actually sold show up, and listings that sat and got delisted vanish from the record. So MLS data leans toward transactions that cleared at or above asking, which pulls median prices up. An assessor working from MLS comps alone is often working from an optimistic sample.

Off-market sales tend to fill in the rest of the picture. The estate sale that closed in two weeks at 8 percent under the neighborhood average. The builder who quietly discounted the last unit in a stale subdivision. The family that sold to a neighbor without an agent to skip the commission. These deals show the real market, more than the marketed-well slice of it.

There's a second reason, and it matters more than people expect. MLS data is proprietary. Walk into a Board of Equalization hearing with a Zillow printout and it carries almost no weight without authentication. A certified copy of a deed, paired with a transfer-tax declaration showing the price, is a government record. It's self-authenticating in most states. That makes it much harder for the assessor's attorney to knock out on foundation grounds.

Where can you find off-market sales data without paying for a subscription?

Start at the county recorder or register of deeds website. In most of the country it's free. Every recorded deed lists the grantor, grantee, date, and legal description. The sale price shows up one of three ways depending on your state: written directly on the deed, calculated from the documentary transfer tax (roughly $1.10 per $1,000 of value in California, for example ^[3]), or stated on a separate excise-tax or transfer declaration that's also public.

Here's the workflow. Open the recorder's parcel search, enter an address within a quarter mile of your home, pull every deed recorded in the 12 months before your lien date, and grab the ones with transfer-tax stamps. Then do the arithmetic. A $385 transfer tax at $1.10 per $1,000 means a $350,000 sale. For Cook County, Illinois and other big jurisdictions, the recorder's database goes back decades and lets you filter by neighborhood or PIN range.

Seven sources are worth your time:

Source	Cost	What you get	Availability
County recorder deed database	Free	Deed date, parties, transfer tax	Nearly universal
State real estate transfer declarations	Free via FOIA	Sale price, property type, conditions	30+ states
County assessor sales tables	Free	Assessor's own sales ratio study data	Many states
PropStream or ATTOM (trial)	$99-$199/mo	Full transaction history, off-market flags	National
Courthouse Retrieval System (CRS)	Varies	Raw deed images	Regional
Sheriff/trustee sale records	Free	Foreclosure auction prices	County-by-county
Neighbor outreach and recorded plat	Free	Confirms who owns adjacent parcels	Local

Don't skip the assessor's own sales data. Many assessors publish the sales they used to calibrate their mass-appraisal model, sometimes called a "sales ratio study" or "use-value study."^[4] Get that list and you can see exactly which sales they weighted and which they threw out. Any arm's-length sale they excluded is a potential argument.

How do you pull deed records and calculate sale price from transfer tax?

The transfer-tax math is simple once you know your state's rate. California charges $1.10 per $1,000 of value (or fraction of it) at the county level, and many cities pile their own tax on top.^[3] Texas collects no transfer tax but requires a sales-disclosure form filed with the county appraisal district. Illinois uses a state rate of $0.50 per $500 plus a county rate that varies.^[5] Florida uses $0.70 per $100 at the state level, with a $0.45 per $100 county surtax in most counties.^[6]

Pull a deed in Los Angeles County that reads $440 in documentary transfer tax. Divide $440 by $1.10, multiply by $1,000, and you get a $400,000 sale price. Write it on your comp sheet next to the address, lot size, square footage, year built, and sale date. That's your raw comparable.

For Los Angeles County property tax appeals, the LA County Assessor's portal lets you search recorded sales by APN, and the transfer tax prints right on the deed image. Santa Clara property tax appeals run the same way through the Santa Clara County Recorder. Montgomery County property tax in Maryland works a little differently: Maryland uses a state transfer tax of 0.5 percent plus local rates, and the price is usually stated on the deed itself rather than inferred from a stamp.

One warning sign. If a deed shows nominal consideration like "$10 and other good and valuable consideration," that's a non-arm's-length sale (a gift or family transfer). Skip it. Those are bad comps, and an assessor will hammer you for using one.

What FOIA or open-records requests get you sales data the assessor actually used?

This is the most underused move in the whole playbook. Every state has a public-records law, and in most of them the assessor's sales files, ratio studies, and mass-appraisal inputs are public records. A tight open-records request can hand you the exact dataset your assessor used to set every value on your block.

The wording carries the weight. Send a written request to the county assessor (or the appraisal district in Texas) asking for three things: all arm's-length sales used in the current assessment cycle within a defined radius of your address; the sales ratio study or qualification report for your property class and neighborhood; and the appraisal card and field notes for your parcel. In Texas, this runs under the Texas Public Information Act (Government Code Chapter 552).^[7] In California, assessor appraisal records are public under Revenue and Taxation Code Section 408, with limited exceptions for confidential income data.^[8]

For Gwinnett County tax assessor and Bexar County tax assessor appeals in Texas, this kind of request is routine and usually answered within 10 business days. In Hennepin County, Minnesota, the comparable sales used in mass appraisal are posted publicly in the assessor's sales study database.^[9] For Hennepin County property tax appeals before the Minnesota Tax Court, that public sales file is often the spine of the taxpayer's entire case.

Keep it narrow. Broad requests get expensive or slow. Name a time window (usually the 12 to 24 months bracketing your lien date) and a boundary (ZIP code, township, or neighborhood code).

How do you select which off-market comps are actually valid for your appeal?

Assessors and hearing officers apply the same filters whether a sale came off the MLS or off the record. The IAAO's Standard on Ratio Studies sets the baseline: sales should be arm's-length, within a reasonable window of the lien date (typically 12 months before through 6 months after, though this varies), and physically close enough to bracket your property.^[2]

The filters that matter:

Proximity. Same subdivision first, then same neighborhood, then same ZIP code. A comp two miles away in a different school district is weak unless you can show the two markets move together.

Time. Closer to the lien date is better. Sales more than 18 months out need time-adjustment work, which invites arguments about market trends. Stay inside the 12-month window if you have enough comps.

Physical similarity. Square footage within 20 percent is a common rule of thumb. Same number of stories, similar lot, similar construction quality (frame versus masonry), same property class (residential versus commercial).

Arm's-length verification. Check the deed for a shared last name. Watch for round-number consideration that smells staged. See if the property turned up on any foreclosure list. The assessor will try to disqualify any comp that looks non-arm's-length.

Once you have five to ten candidates, rank them by proximity and similarity, then present the three to five best. More is not stronger. A tight set of three highly similar sales beats a scatter of ten marginal ones every time. The TaxFightBack DIY appeal kit includes a comp-grid template laid out the way hearing officers expect to read it.

Honest caveat: nobody has clean data on success rates by comp quality. The closest published research is from the Lincoln Institute of Land Policy, which finds that taxpayers who present three or more comparable sales with physical adjustments win at meaningfully higher rates than those who present only an opinion of value. Exact percentages swing by jurisdiction.^[10]

What adjustments do you need to make to off-market comps?

Raw sale prices almost never compare cleanly. A house that sold for $310,000 doesn't prove yours is worth $310,000 unless the two are basically twins. You adjust, in dollars or percentages, for every difference between each comp and your property.

The standard categories: gross living area (roughly $50 to $150 per square foot depending on the market, but use local paired-sales data if you can find it), lot size, garage (one car versus two, attached versus detached), condition, age, and features like a pool or finished basement. The IAAO and most state assessment manuals publish adjustment grids, and some county assessors publish their own.^[2]

The rule that decides your appeal: your adjustments should net to a value below your assessed value. If your best comp lands at $325,000 after adjustments and you're assessed at $380,000, that gap is the case. Put the adjusted grid on one page, show your math, and let the numbers do the talking.

Don't over-adjust. Every adjustment is an assumption a hearing officer can attack. Adjust five factors across five comps and you've stacked 25 assumptions on the table. Limit yourself to the two or three factors that actually move value for your property. In most residential appeals, square footage and lot size explain about 80 percent of the difference.

How do different states handle sales disclosure and what does that mean for your research?

Sales disclosure laws swing hard from state to state, and they decide how much free data you can pull. States sort into three rough groups.

Full-disclosure states put the actual sale price on the deed or a companion form that's a public record. Michigan, Wisconsin, and New York are examples. Anyone can look up any price at the county recorder's office or online. For NYC property tax appeals, the NYC Department of Finance publishes recorded sales quarterly, searchable online by block and lot.^[11]

Transfer-tax states don't put the price on the deed, but they list the documentary transfer tax, and you back-calculate the price as shown above. California, Florida, and Illinois run this way.

Non-disclosure states are the hard cases. In Alaska, Idaho, Kansas, Louisiana, Mississippi, Missouri, Montana, New Mexico, North Dakota, Texas, Utah, and Wyoming, sale prices aren't required to appear in any public document.^[12] In Texas, the appraisal district is actually barred from using a non-disclosed sale as the primary basis for value, which cuts both ways: you can't easily find prices, but neither can the district. In these states, PropStream, ATTOM, or a licensed appraiser with MLS access earns its cost.

For St. Louis County personal property tax appeals in Missouri (a non-disclosure state), the workable path is an MAI appraisal or the assessor's own sales data, which the assessor must produce on request even when the underlying deals aren't individually disclosed.

Can you use foreclosure sales, short sales, or estate sales as comps?

This is genuinely contested ground, and the answer depends on your jurisdiction's rules and the facts of each sale.

Foreclosure auction sales (trustee sales, sheriff sales) usually get pulled from mass-appraisal datasets because they're presumed non-arm's-length. A lender under a legal obligation to sell isn't a "typically motivated seller" under the IAAO definition.^[2] But if your neighborhood took a wave of foreclosures and those homes are now in the hands of arm's-length buyers who resold them, those REO resales work fine as comps. The second transaction (investor to retail buyer) is fully arm's-length.

Short sales sit in a gray zone. Many appraisers treat them as arm's-length if the lender approved the price after real market exposure, the buyer had no insider tie to the seller, and the sale had no unusual conditions. Some assessors toss them automatically. Want to use one? Come with the market-exposure evidence.

Estate sales are often arm's-length and fully usable. The executor has a fiduciary duty to get the most for the estate, so the motivation element holds. Probate court records are public and let you confirm the sale wasn't between family members.

The honest read: when you're unsure a sale survives a challenge, keep it in your backup and lead with cleaner comps. Save the contested ones for rebuttal if the assessor goes after your primary set.

What does a finished comp grid look like, and what format should you bring to the hearing?

Hearing officers see dozens of appeals a day. A grid built in the format they already use actually gets read. Give it one row per comparable sale and one column per attribute. At minimum:

• Property address and APN
• Sale date
• Sale price (and source: deed book/page, or transfer-tax calculation)
• Gross living area (sq ft)
• Lot size
• Year built
• Price per square foot
• Dollar adjustment for major differences from the subject
• Adjusted sale price

At the bottom, show the range and average of adjusted prices against your current assessed value. If the average adjusted price is $312,000 and your assessment is $380,000, that one line tells the story.

Bring printed copies. One for you, one for the hearing officer, one for the assessor's rep. Some jurisdictions make you submit evidence in advance (often 5 to 10 days before the hearing), so check your local rules. The TaxFightBack appeal kit includes a pre-formatted comp grid in Excel that runs the adjustments for you, which helps if spreadsheets aren't your idea of a good time.

For large-county appeals you file online, like LA County property tax or Gwinnett County, upload the grid as a PDF with your evidence package. Label it plainly: "Comparable Sales Grid - [Your Address] - [Tax Year]."

How do you find comps for unusual properties that rarely sell?

Rural acreage, historic buildings, mixed-use properties, and homes with heavy deferred maintenance all run into thin comparable-sale markets. When direct comps are scarce, you still have options.

Expand the radius slowly and document why each step is justified. A rural property might need comps from a 10-mile radius instead of a quarter-mile. The trick is showing the wider area is the same market, not a different one. Land-use maps, school district lines, and local market reports help you make that case.

Expand the time window and apply time adjustments. If you find only two sales inside 12 months but five inside 24, use the older ones with a time adjustment tied to a local price index. The Federal Housing Finance Agency publishes quarterly house price indexes by metro area and state that are free, government-sourced, and credible in a hearing.^[13]

For commercial or mixed-use properties where income drives value, the income capitalization approach often beats a direct sales comparison anyway. If you have actual lease income below market (a long-term tenant paying under market rent, say), lead with the income approach and use any available sales as corroboration.

For Bibb County tax assessor appeals in Georgia or similar rural counties, the Georgia Department of Revenue publishes county-level property sales data that covers transactions smaller-county assessors may not track on their own.^[14]

What mistakes do homeowners make when presenting comps, and how do you avoid them?

The most common mistake is using the wrong date. Your comps have to bracket the lien date. If your lien date is January 1, 2024, an August 2024 sale may be inadmissible, or at least attackable, in many states. Check your state's statute on the permissible window.

Second mistake: confusing assessed value with market value. If a neighbor's assessment sits below yours, that's an assessment inequity argument (a separate and sometimes easier path), not a market value argument. Don't mix the two theories in one presentation unless your jurisdiction allows an equity claim.

Third: skipping the physical similarity analysis. If your comp is 400 square feet bigger than your home but sold for the same price, and you don't adjust, the assessor's rep will adjust for you, and the adjusted number will land above your assessment.

Fourth: too many comps. Five well-chosen, well-adjusted sales beat fifteen mediocre ones. A long list signals you couldn't find three strong ones.

Fifth: confusing list price with sale price. List prices aren't comps. Only recorded sale prices from completed arm's-length deals count. Never cite a Zestimate or a pending-sale price as evidence.

Frequently asked questions

What is an off-market comparable sale for property tax purposes?

Any arm's-length real estate transaction recorded in the public deed record that was never listed on a multiple-listing service. Estate sales, neighbor-to-neighbor deals, and builder sales to first buyers all qualify. For property tax appeals, assessors are required to value property based on all qualifying arm's-length sales, so off-market transactions carry the same legal weight as MLS-listed ones.

How do I find recent home sales in my neighborhood for free?

Go to your county recorder or register of deeds website and search by address or parcel number within your neighborhood. Most county recorder portals are free and let you filter by recording date. If your state collects documentary transfer tax, you can calculate the sale price from the tax stamp on the deed. Georgia, Michigan, and Wisconsin also publish statewide sales databases at no charge.

What is a documentary transfer tax and how do I use it to find sale prices?

A documentary transfer tax is a government fee charged when real property changes hands, usually based on the sale price. California charges $1.10 per $1,000 of value at the county level. Divide the tax amount on the deed by your state's rate to back-calculate the sale price. This works in California, Florida, Illinois, and most other transfer-tax states, giving you free access to sale prices on every recorded deed.

Can I use an FOIA or public-records request to get the assessor's sales data?

Yes. In most states, the comparable sales the assessor used to calibrate the mass-appraisal model are public records. Request the assessor's sales qualification report, ratio study, and field notes for your parcel. In Texas, use the Texas Public Information Act (Government Code Chapter 552). In California, use Revenue and Taxation Code Section 408. Most agencies must respond within 10 business days.

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

Three to five strong, well-adjusted comps is the practical target for residential appeals. More is not better if the extra sales are weaker. A tight set of three highly similar sales within a half-mile, all showing adjusted values below your assessment, beats ten loosely matched sales from across the county. Hearing officers read dozens of cases a day and reward clarity.

Are foreclosure sales or estate sales valid as comps in an appeal?

Estate sales are generally valid because the executor has a fiduciary duty to maximize proceeds, which satisfies the arm's-length test. Foreclosure auction sales are usually excluded as non-arm's-length. REO resales (where the bank sells to a retail buyer after taking back the property) are typically valid. Short sales sit in a gray zone; check your county's sales-qualification rules before relying on one.

What adjustments do I need to make to comparable sales?

Adjust for differences in gross living area, lot size, garage, age, condition, and material features between each comp and your property. Apply a dollar or percentage adjustment per difference so the comp reflects what it would have sold for if identical to your home. Limit adjustments to the two or three factors that matter most; over-adjusting creates unnecessary vulnerabilities at the hearing.

What if I live in a non-disclosure state where sale prices are not public?

In the 12 non-disclosure states (including Texas, Missouri, and Utah), you cannot calculate sale prices from public deeds. Your options: use the assessor's own sales data (which they must produce on request even in non-disclosure states), subscribe to PropStream or ATTOM for 30 to 90 days, or hire a licensed appraiser with MLS access. Texas appraisal districts are also restricted from using non-disclosed sales as the sole basis for value.

How close to my assessment lien date do comparable sales need to be?

Most states require comps within 12 months before the lien date, and many allow sales up to 6 months after. Older sales require a time adjustment backed by a credible price index, such as the FHFA House Price Index. Using stale comps without a time adjustment is a common mistake assessors exploit. Check your state's specific statute for the permissible window.

Can I use sales from a neighboring subdivision or ZIP code as comps?

Yes, if you can show the two areas are the same market. Supporting evidence includes similar school districts, comparable median incomes, similar zoning, and similar price-per-square-foot trends. Start with comps from your own subdivision. Move outward only when the immediate market lacks enough sales, and document each expansion step in your written submission.

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

A sales ratio study compares each property's assessed value to its actual sale price to measure assessment uniformity. If the median ratio in your neighborhood is 95 percent but yours is 115 percent, you have an equity argument independent of market value. Most state assessment laws require ratios within a defined band, often 90 to 110 percent. Requesting the assessor's ratio study for your property class is free and often reveals systematic over-assessment.

What format should my comp grid be in when I present it at the hearing?

One page, tabular format: one row per comparable sale, columns for address, APN, sale date, sale price, square footage, lot size, year built, price per square foot, dollar adjustments, and adjusted sale price. Show the range and average of adjusted prices at the bottom against your assessed value. Bring three printed copies: one for yourself, one for the hearing officer, one for the assessor's representative.

How do I find comps for unusual or rural properties that rarely sell?

Expand your search radius gradually and document why the wider area is the same market (same zoning, same school district, same land use). Expand your time window to 24 months and apply a time adjustment using the FHFA House Price Index for your state or metro. For commercial properties, consider the income approach as the primary method and use available sales as corroboration. Georgia's Department of Revenue publishes statewide sales data covering rural counties.

Does using off-market comps give me an advantage over the assessor?

It can. Mass-appraisal models lean heavily on MLS-sourced data, which skews toward successfully-marketed homes. Off-market sales, especially estate sales and quiet neighbor deals, often fall at the lower end of the price range. If those transactions are arm's-length and you document them properly, they represent legitimate market evidence the assessor's model may have missed or discounted.

Sources

1. International Association of Assessing Officers, Standard on Mass Appraisal of Real Property: Assessors derive market value from all arm's-length sales, not only MLS-listed transactions.
2. International Association of Assessing Officers, Standard on Ratio Studies: An arm's-length sale is one in which the buyer and seller are typically motivated, well-informed, and acting in their own best interests, without undue pressure or unusual terms; sales should fall within 12 months of the lien date for primary use.
3. California State Board of Equalization, Documentary Transfer Tax: California charges $1.10 per $1,000 of value (or fraction thereof) in county-level documentary transfer tax, allowing back-calculation of sale price from the deed.
4. California State Board of Equalization, Assessment Practices Survey Program: County assessors publish sales ratio studies and use-value studies used to calibrate mass-appraisal models; these documents are public records in California.
5. Illinois Department of Revenue, Real Estate Transfer Tax: Illinois imposes a state real estate transfer tax of $0.50 per $500 of value plus a county rate that varies.
6. Florida Department of Revenue, Documentary Stamp Tax: Florida charges $0.70 per $100 of consideration at the state level and a $0.45 per $100 county surtax in most counties, recorded on deeds.
7. Texas Office of the Attorney General, Texas Public Information Act (Government Code Chapter 552): The Texas Public Information Act (Government Code Chapter 552) entitles requesters to government records including appraisal district sales files; agencies must respond within 10 business days.
8. California Revenue and Taxation Code Section 408, California Legislative Information: California Revenue and Taxation Code Section 408 makes county assessor appraisal records public, with limited exceptions for confidential income data.
9. Hennepin County Minnesota Assessor, Sales Study Database: Hennepin County publishes comparable sales used in mass appraisal publicly in an online sales study database accessible to taxpayers.
10. Lincoln Institute of Land Policy, Property Tax Assessment Research: Research from the Lincoln Institute of Land Policy shows taxpayers who present multiple comparable sales with physical adjustments achieve higher appeal success rates than those presenting only an opinion of value, though exact rates vary by jurisdiction.
11. New York City Department of Finance, Rolling Sales Data: The NYC Department of Finance publishes recorded property sales quarterly, searchable online by borough, block, and lot.
12. National Association of Realtors, Real Estate Non-Disclosure States List: Twelve U.S. states, including Alaska, Idaho, Missouri, Texas, and Utah, do not require public disclosure of sale prices on recorded deeds or companion transfer documents.
13. Federal Housing Finance Agency, House Price Index (HPI): The FHFA publishes quarterly house price indexes by metro area and state, providing a government-sourced benchmark for time-adjusting comparable sales in property tax appeals.
14. Georgia Department of Revenue, Property Tax Division: The Georgia Department of Revenue publishes county-level property sales data covering transactions that rural-county assessors may not independently track.