How recent do comparable sales need to be for a tax appeal?

Last updated 2026-07-09

What's the short answer on comp recency?

It depends on the state, and sometimes on the county or the individual hearing officer. That's the honest answer. But one practical rule holds up almost everywhere.

Sales that closed within 12 months before your assessment date are accepted without argument. Sales older than 24 months almost always need explanation and adjustment. Between 12 and 24 months sits a gray zone where you have to show your work.

The International Association of Assessing Officers (IAAO) sets the professional standards most assessors and appeal boards follow. Its Standard on Ratio Studies recommends using sales from a 12-month period centered on the assessment date when possible. ^[1] Many state statutes copied that guidance almost word for word.

Find three to five arms-length sales within 12 months and stop. That's your case.

Why does the assessment date matter so much?

Every jurisdiction freezes property value on one specific date for a given tax year, and your comps have to bracket that date. Not your hearing date. Not the day your tax bill showed up. Pick the wrong anchor and your best comps become irrelevant.

New York State uses a taxable status date set by each municipality, often March 1 for towns. ^[2] Illinois uses January 1. California's Proposition 13 system runs on a base year value, with supplemental assessments keyed to the date of change of ownership. ^[3]

Here's a concrete example. Say you own a home in Cook County and your assessment rests on a January 1, 2024 valuation date. A sale that closed in November 2023 is excellent evidence. A sale that closed in January 2025 (a year after the valuation date) is weaker than it looks, because it reflects market conditions that didn't exist on the date being assessed. Boards split on whether they'll take post-assessment sales at all, though many accept them as trend evidence.

For more on how Cook County handles assessments and appeals, see our article on the cook county tax assessor tax bill.

Does each state have a specific comp recency rule?

Many do, and the differences are real enough that reading your state's statute is worth 20 minutes. Here's a breakdown of several major states with their requirements or common practice:

State	Valuation Date	Comp Window (statute or board guidance)	Source
New York	Taxable status date, varies by municipality	Typically 12 months before valuation date	NY RPTL § 306 [2]
Illinois	Jan 1	12 to 24 months commonly accepted; PTAB allows older with adjustment	35 ILCS 200/1-130 [4]
Texas	Jan 1	Sales from prior 24 months; 12 months preferred by most ARBs	Texas Tax Code § 23.013 [5]
California	Jan 1 (or change of ownership)	Usually 6 to 12 months before lien date	Cal. Rev. & Tax Code § 110 [3]
Florida	Jan 1	Qualified sales from prior calendar year strongly preferred	Fla. Stat. § 193.011 [6]
Georgia	Jan 1	Prior 3 years allowed by statute, but recent 12 months dominate	OCGA § 48-5-2 [7]
New Jersey	Oct 1 (prior year)	2-year period ending on valuation date is standard	N.J.S.A. 54:4-23 [10]

Georgia formally allows three years of sales history. That's an outlier, and even there the board leans hard on recent sales. Texas allows 24 months, but most Appraisal Review Boards look at anything older than 18 months with open doubt unless you explain a thin market.

If your state isn't in this table, search your property tax code for "qualified sales" or the definition of "market value." That section almost always carries a time constraint, spelled out or implied.

What happens if I can only find older comparable sales?

You still have options. Don't drop the appeal just because your neighborhood went quiet for a year.

The standard professional move is a time adjustment, sometimes called a market conditions adjustment. You take the older sale price and move it forward (or backward) to reflect what the market did between the sale date and your assessment date. Appraisers do this constantly, and boards know the method.

To make a time adjustment credible, bring data. The Federal Housing Finance Agency's House Price Index publishes quarterly price changes down to the metropolitan area. ^[8] If the FHFA shows home prices in your metro rose 6% between an older sale and your assessment date, you apply that 6% to the sale price and argue the adjusted figure represents value on the assessment date.

A few cautions. Don't cherry-pick an index that flatters your number; choose one and apply it the same way to every comp. Some boards reject time adjustments outright when the market was volatile during the adjustment period, because the uncertainty swamps any precision. And if you're adjusting a comp by more than 15 to 20%, the board may throw it out entirely. At that point you're better off arguing thin market conditions and asking for a continuance.

For appeals in high-volume urban markets where older data is common, see how assessors handle it in la county property tax and nyc property tax.

How many comparable sales do I actually need?

Three is the informal floor most boards expect. Five is comfortable. Fewer than three invites the assessor's attorney to argue your evidence is too thin to rebut the presumption of correctness the assessment carries.

That presumption is real, and it shifts the burden onto you. In most states the assessed value is presumed correct until you prove otherwise. ^[4] Three solid recent comps usually clears that bar in a residential appeal. Commercial property is different; you'll often need a full appraisal.

Quality beats quantity every time. One sale two blocks away, closed three months before the assessment date, on a house nearly identical to yours in size, age, condition, and lot, beats five scattered sales that each need heavy adjustment.

Two things to avoid. Distressed sales (foreclosures, short sales, estate sales under financial pressure) and sales between related parties. Most state statutes exclude these from the definition of qualified or arms-length sales. ^[5] Slip one in and you hand the hearing officer a reason to doubt everything else you brought.

What makes a comparable sale truly comparable?

Recency is one dimension. The sale also has to be physically and legally similar to your property. Appraisers work through four adjustment categories:

1. Location. Same neighborhood or comparable market area. Crossing a school district boundary can swing value 10 to 15% in some markets. 2. Physical characteristics. Gross living area, bedroom and bathroom count, lot size, age, condition. Rule of thumb from appraisal practice: adjustments over 25% of the sale price on a single comp mean it probably shouldn't be used. ^[1] 3. Transaction conditions. Arms-length, market-rate financing, no odd concessions. If the seller kicked in $20,000 toward the buyer's closing costs, the net price needs adjusting. 4. Market conditions (time). Covered above. It comes after the other adjustments, not before.

At the hearing, present your comps on a simple grid: property address, sale date, sale price, adjusted price, and a note on what you adjusted and why. You don't need appraisal software. A clean spreadsheet with honest, conservative adjustments does the job. Padding adjustments to improve the numbers backfires the moment the assessor's representative pulls the MLS data.

Assessors in high-stakes counties like santa clara property tax and montgomery county property tax reviews often bring printed comp grids to hearings. Match their format and you read as prepared.

Can I use pending sales or listing prices as evidence?

Almost never as primary evidence. A listing price is an asking price, and asking prices routinely miss actual sale prices by 5 to 15%. Pending sales haven't closed, so the final number isn't known yet.

Some boards in soft markets accept active listing data as context, not as a comp in the formal sense. The better use of listings: show that comparable homes have sat 90 to 120 days with multiple price cuts. That tells a story about demand that supports your case even when nothing has sold.

Post-assessment sales occupy a middle ground. Most boards will consider them as directional evidence, especially if your assessment date was six months ago and the market has slid since. The argument is that a downward trend already existed on the assessment date and the later sale confirms it. It's a harder argument to win, and it needs at least one truly contemporaneous comp to anchor it.

How do I find recent comparable sales for my appeal?

You have several free or cheap sources.

County assessor or recorder websites. Most publish recent sales data online, and many link straight to recorded deeds with sale prices. This is the same data the assessor used to set your value, and it's public. ^[9]

Zillow and Redfin. Both show recent sold prices with dates and basic property details. Not perfect, but fast for a first pass to see what exists.

Free MLS access. Many title companies and real estate attorneys will pull a basic comp report at no charge if you ask. Agents sometimes do it hoping for future business. MLS data is cleaner than third-party aggregators.

FHFA House Price Index. Useful for the time-adjustment math when your market has few recent sales. ^[8]

Court records. Some jurisdictions post sales from probate, tax sales, and other court-ordered transfers. These are usually non-arm's-length, but reviewing them shows you what to exclude.

For county-level guidance on where to look, our articles on gwinnett county tax assessor and bexar county tax assessor walk through the local databases in those markets.

What do assessors do when they challenge my comps?

Expect the assessor's office to question three things: sale date, arms-length status, and comparability.

On sale date, they'll call anything older than 12 months stale. Have your time-adjustment method ready if you're leaning on older sales.

On arms-length status, they may pull the deed or transfer records to show the parties were related or the sale had strings attached. Know each comp well enough to explain it cold.

On comparability, they'll point to gaps in square footage, lot size, or condition and argue the adjustment should be bigger, which pushes your indicated value up. Your best defense is comps so physically similar that big adjustments never come up.

The assessor may also bring their own comps, usually chosen to support the assessed value. You have the right to question those in the hearing. Ask for the sale date, the proximity, the physical characteristics. If any of their comps are non-arm's-length, say so. Many residential hearing boards are not trained appraisers, and a calm, organized takedown of a bad comp carries weight.

One practical tip: print everything. Don't assume the hearing officer has your digital submission open or has read a word of it.

Is there a tool that helps you organize this evidence without hiring anyone?

The TaxFightBack DIY appeal kit includes a comp analysis worksheet built to match the grids most state boards expect, plus a state-by-state guide to valuation dates and comp windows. It won't file for you or argue for you. It structures your evidence so the hearing officer follows your logic without you narrating the methodology from scratch.

The kit is optional. Everything you need to build a solid comp case is public. The IAAO guidance is free to download, county sale records are public, and the FHFA HPI is a government database. Be methodical and you can build a case as strong as any contingency firm's, and you keep 100% of the reduction instead of handing over a cut.

Here's the money math. Contingency firms typically charge 25 to 40% of your first-year tax savings, and some take a slice for multiple years. On a $3,000 reduction, that's $750 to $1,200 out of your pocket. The case for doing it yourself is mostly financial, as long as you stay organized.

What's the biggest mistake people make with comps on appeal?

Using comps that are recent but not comparable, or comparable but not recent. Both errors come from the same habit: grabbing whatever's available instead of being selective.

The second-biggest mistake is stacking up mediocre comps instead of picking three excellent ones. A wall of shaky data reads as desperation. Three clean, well-documented, physically similar, recent sales read as competence.

The third is ignoring the burden of proof. You have to overcome the presumption that the assessment is right. Your comps need to show a value clearly below the assessed value after every adjustment, not a hair below. Boards get skittish about shaving an assessment by a couple of percent when there's uncertainty; they'll split the difference or deny the appeal. Aim for comps that point to a value at least 10 to 15% under your assessed value, so there's room for that negotiation.

And don't forget that bibb county tax assessor and similar smaller jurisdictions sometimes run informal processes where a simple letter with three good comps settles it before any formal hearing. Check whether your county offers an informal review step first.

Frequently asked questions

How recent do comparable sales need to be for a property tax appeal?

The standard most boards apply is sales within 12 months before the assessment date. Sales within 6 months are stronger. Sales from 12 to 24 months ago are acceptable in most states if you apply a documented time adjustment for market changes. Anything older than 24 months faces skepticism unless the market had very few transactions, and you'll need to explain the methodology clearly.

Can I use sales from after my assessment date as comparables?

Most boards allow post-assessment sales as supporting or corroborating evidence, but not as primary comps. The legal question is what the property was worth on the assessment date, not later. Post-assessment sales work best when you pair them with at least one contemporaneous comp and use the later sale to show a price trend that already existed at the assessment date.

What is the assessment date and how do I find it?

The assessment date is the specific calendar date your jurisdiction uses to freeze property value for a given tax year. Common dates are January 1 (most states) or October 1 (New Jersey). Your county assessor's website or your property tax bill usually lists the "lien date" or "valuation date." Your comp sales need to bracket this date, not the date of your hearing or your tax bill.

What if there were no home sales near me in the past year?

Use what's available, apply a time adjustment using the FHFA House Price Index for your metro area, and document your methodology clearly. Also argue to the board that thin market conditions limit the data and that the assessor bore a responsibility to be conservative in that environment. Some boards will accept sales from 18 to 36 months back if you explain the market conditions and show your adjustment work.

Do foreclosures count as comparable sales for a tax appeal?

Generally no. Most state statutes define qualified or arm's-length sales to exclude foreclosures, bank-owned sales, and other distressed transfers. Using them as comps can damage your credibility with the hearing officer. You can, however, reference a high foreclosure rate in the neighborhood as market context to support a downward trend argument, even without using those prices directly as comps.

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

Three is the practical minimum for residential appeals. Five is comfortable. The number matters less than the quality. Three physically similar, recent, arm's-length sales within a half-mile of your property will outperform eight distant or adjusted sales. For commercial property, a full appraisal is typically required; comparable sales alone rarely satisfy the evidentiary standard.

Can I use Zillow or Redfin data for tax appeal comparables?

Yes, for a first pass to identify candidates. The actual evidence you present should come from county recorder records or MLS data, which is cleaner and harder to dispute. Boards are familiar with Zillow and some will accept printed Zillow sold pages, but pulling the deed from the county recorder and showing the recorded sale price is more authoritative.

What adjustments can I make to comparable sales to account for differences?

Standard adjustments cover location, gross living area, lot size, bedroom and bathroom count, age, condition, and market conditions (time). Apply each adjustment conservatively and document your reasoning. A rule of thumb from appraisal practice: if your total net adjustment on a single comp exceeds 25% of its sale price, that comp is probably too different to be reliable and you should find a better one.

Do different states have different rules about how old comps can be?

Yes. Georgia statute formally allows sales from the prior three years. Texas allows 24 months. Florida and New York boards strongly prefer sales within 12 months. Illinois's Property Tax Appeal Board accepts older sales with documented adjustment. Always check your state's property tax code for the phrase 'qualified sales' or the market value definition, which usually implies or specifies a time window.

Can I use my neighbor's sale price as a comp even if it sold two years ago?

You can use it, but you'll need a time adjustment backed by data like the FHFA HPI for your metro area. Two years is at the edge of what most boards find credible, so pair it with any more recent sales you can find, even if they're farther away. A neighbor's sale with a time adjustment plus a closer but older sale from a similar property is a reasonable combined argument.

What does 'arm's-length transaction' mean for tax appeal purposes?

An arm's-length sale is one between unrelated, financially independent parties, each acting in their own interest, with no unusual pressure or concessions. Sales between family members, employer-to-employee transfers, foreclosure sales, estate sales under financial distress, and sales with large seller concessions typically don't qualify. Most state statutes define this explicitly, and using a non-arm's-length sale as a comp is a fast way to lose credibility at a hearing.

What if the assessor brings better comps than mine to the hearing?

Ask questions. Find out the sale date, proximity, and physical characteristics of each comp they present. If any are non-arm's-length, flag it. If any required large adjustments that weren't disclosed, raise it. You have the right to respond to evidence presented at the hearing in most jurisdictions. Staying calm and methodical is more effective than arguing; hearing officers notice when one side is organized and the other is scrambling.

Should I hire a contingency firm or do this myself?

Contingency firms typically charge 25 to 40% of your first-year savings, sometimes more. On a $3,000 tax reduction, that's $750 to $1,200 paid to someone else for gathering the same public sales data you can access yourself. The DIY case is strong if you're organized. The cases where a contingency firm may genuinely add value are complex commercial properties requiring a full appraisal and expert testimony.

Sources

1. International Association of Assessing Officers (IAAO), Standard on Ratio Studies: IAAO recommends using sales from a 12-month period centered on the assessment date; adjustments exceeding 25% of sale price signal a comp may be unsuitable
2. New York State Legislature, Real Property Tax Law § 306: New York uses a specific taxable status date for each municipality, establishing the legal valuation date for property tax purposes
3. California State Board of Equalization, Revenue and Taxation Code § 110: California defines full cash value with reference to the lien date and recent open-market transactions
4. Illinois Property Tax Appeal Board, 35 ILCS 200/1-130: Illinois defines market value and the presumption of correctness for assessed values; PTAB accepts sales from 12 to 24 months with adjustment
5. Texas Comptroller of Public Accounts, Texas Tax Code § 23.013: Texas Tax Code defines arm's-length sales and the use of sales from the prior 24 months for mass appraisal; excludes distressed sales from qualified sales
6. Florida Department of Revenue, Florida Statutes § 193.011: Florida statute specifies factors in deriving just value including bona fide sales in the prior year, establishing the 12-month preference for comp recency
7. Georgia Department of Revenue, Official Code of Georgia Annotated § 48-5-2: Georgia statute defines fair market value using sales and allows consideration of sales from the prior three-year period
8. Federal Housing Finance Agency, House Price Index: FHFA HPI publishes quarterly price change data by metropolitan statistical area, usable for time adjustments in property tax appeals
9. National Association of Counties, County Assessor Data Resources: Most county assessors publish recent sales data online from recorded deeds, which is the same data used in the assessment process
10. New Jersey Division of Taxation, N.J.S.A. 54:4-23: New Jersey uses October 1 of the prior year as the assessment date and applies a two-year sales study period for ratio analysis