Is My House Over-Assessed? A 20-Minute Self-Check for Any State (2026)

Roughly one in five homes is assessed above what comparable homes in the same neighborhood are carrying.

That is not a marketing figure. We ran the comparison across 4,836,570 residential properties in 14 Texas counties for our over-assessment study: 1,000,060 of them, about 21%, sit more than 5% above the comparable homes in their own appraisal neighborhoods, totaling roughly $1.5 billion a year in excess property tax. The counties involved are among the most sophisticated appraisal operations in the country. The error rate is not a scandal, it is just what mass appraisal produces at scale.

Which raises the only question that matters to you: is your house one of them?

You can find out yourself. This guide walks through five tests, in order of how much evidence they give you per minute spent. All five use free public data. None of them require buying anything.

Or skip to the answer. AppealMyTax runs tests 2 and 3 automatically against 22.7 million real county parcel records and shows you the result before you pay anything. Check your address free →

Before you start: get the right number

Pull your most recent assessment notice, or find your parcel on your county assessor's website. You are looking for the assessor's opinion of market value, which your state may call just value, actual value, fair market value, appraised value, or full value.

Do not use the assessed value unless you are in a state that assesses at 100% of market. In Georgia the assessed value is 40% of market value. In Cook County it is 10%. In Colorado it is a single-digit percentage. An assessed value that looks low can be sitting on top of a market claim that is far too high. If your state uses a ratio, divide the assessed value by that ratio first. Our guide to assessed value vs market value covers the conversion state by state.

Also write down: your square footage, year built, bed and bath count, lot size, and the prior year's value.

Test 1: The purchase price test (2 minutes)

If you bought this home within roughly the last 18 months in a normal, arm's length sale, compare your closing price to the county's market value.

If the county's number is meaningfully above what you actually paid, you have the single most persuasive piece of evidence available in a property tax appeal. An arm's length sale is the definition of market value. You did not estimate it, you transacted it.

This test wins hearings on its own more often than any other. It is also the test recent buyers most often skip, because they assume the county simply used their purchase price. Frequently it did not, especially in the states where sale prices are not publicly disclosed.

Two disqualifiers to be honest about: a foreclosure, short sale, auction, estate sale, or purchase from a relative is not an arm's length transaction and carries far less weight. And if you bought two years ago in a rising market, the county may be right that the property is worth more now.

Flag it if: the county's market value exceeds your recent arm's length purchase price by more than about 5%.

Test 2: The uniformity test (10 minutes, the one that matters most)

This is the test that found a million over-assessed homes in our study, and the one most homeowners never run.

Compare your assessed value per square foot to that of similar homes near you.

Here is why it is powerful. You do not have to prove what your home is worth, which is a subjective argument you can lose. You only have to prove that your home is being treated differently from comparable homes, which is arithmetic from the county's own published records. Several states, Texas most explicitly, make this a completely independent legal ground for appeal, separate from market value.

How to run it:

1. Go to your county assessor's property search and find 6 to 10 homes near you (same subdivision or within about half a mile) that are genuinely similar: within roughly 15% of your square footage, within about 10 years of your build year, same style, similar lot.
2. For each, record the assessor's market value and the square footage.
3. Divide value by square footage to get value per square foot.
4. Take the median of those comparable figures, and compare it to yours.

If comparable homes are carrying $170 per square foot and your parcel is at $210, the county is valuing your house 24% higher per square foot than its neighbors. That is your case, and it is built entirely from the county's own data, which the county cannot easily dispute.

Flag it if: your value per square foot is more than about 10% above the median of genuinely comparable neighbors.

This test is tedious by hand, which is precisely why we automated it. Our calculator does this against real county roll data and shows you the comparable properties and the gap before asking you for anything.

Do not want to build a spreadsheet? AppealMyTax pulls your parcel and comparable homes from the county roll and shows you the per-square-foot gap in about 30 seconds, free. If there is a case, the $49 report hands you the whole comparison as a filing-ready PDF. Flat fee, and you keep 100% of your savings. Run the check →

Test 3: The property card audit (5 minutes, highest fix rate)

Pull your property record card from the assessor's website and check every physical fact against reality.

The mass appraisal model is only as good as the data it runs on, and county records carry errors at a meaningful rate. Verify:

• Square footage. The most common and most valuable error. Counties sometimes include unfinished basements, attached garages, enclosed porches, or a permitted addition that was never built. Measure if you have any doubt.
• Bedroom and bathroom count. A phantom bathroom is worth real money in a valuation model.
• Year built. Affects the depreciation and quality schedule.
• Lot size. Compare to your deed or survey.
• Features. A pool that was removed, a fireplace you do not have, central air that was never installed, a finished basement that is not finished.
• Condition or quality grade. Some counties publish this. If yours is coded "good" and the kitchen is original 1979, that is worth challenging.

A factual error is the best possible finding. You are not arguing opinion against a professional, you are pointing at something that is simply wrong. Most counties will correct clear factual errors through an informal review, without a hearing, sometimes with a phone call and a photo.

Flag it if: any physical characteristic on the card is wrong in a direction that inflates value.

Test 4: The year-over-year jump test (2 minutes)

Compare this year's market value to last year's, and compare that increase to what your local market actually did.

If the county raised your value 22% in a year when local sales were up 6%, something specific happened to your parcel: a reassessment cycle, a neighborhood factor applied broadly, a permit that triggered a review, or a data change. It does not automatically mean the new value is wrong, but a large jump that outruns the market is worth investigating, and it is often the result of a model recalibration that overshot on some parcels.

Be careful in capped states. In Texas and Florida, the assessed value is limited (10% a year for a Texas homestead, 3% or CPI for a Florida homestead) while the market or just value underneath is not. A modest assessed increase can be sitting on a large market value increase. Look at the uncapped number.

Flag it if: your market value rose substantially faster than comparable local sales.

Test 5: The county accuracy test (5 minutes)

Look up whether your county meets the professional standards assessors are measured against.

The International Association of Assessing Officers publishes the accuracy standards used across the industry. From the IAAO Standard on Mass Appraisal of Real Property:

• Level of appraisal: the median assessment ratio should be between 0.90 and 1.10, meaning the county should assess homes at 90% to 110% of actual sale prices.
• Coefficient of dispersion (COD): measures consistency within a group of properties. The standard is 5 to 10 for newer or fairly similar single-family homes and condominiums, and 5 to 15 for older or more heterogeneous areas. A higher COD means assessments in that group are scattered, which means some are badly wrong.
• Price-related differential (PRD): should be 0.98 to 1.03. Above 1.03 indicates regressivity, where assessment ratios fall as property values rise.

Most states publish an annual ratio study or equalization report with these statistics by county and property class. Search for "[your state] ratio study" or "[your state] equalization report."

Two things to take from this. First, if your county's residential COD exceeds the standard, that is a published, official admission that assessments there are inconsistent, and it is legitimate context to cite at a hearing. Second, and more useful: regressivity is common, and it means ordinary homes are often assessed at a higher fraction of their true value than expensive ones. If you have been assuming over-assessment is a problem for people with bigger houses, the industry's own literature says the opposite is the more frequent pattern.

Scoring your results

• Zero flags. You are probably fairly assessed. That is genuinely useful to know, and it cost you 20 minutes. Re-run it next year when new values are issued, because the answer changes annually.
• One flag, small. Borderline. If it is a property card error, still report it, since factual corrections are usually free and quick.
• Two or more flags, or any single gap above 10%. Worth filing. Assemble the evidence and file before your deadline.

One reassurance that removes most of the hesitation: in the overwhelming majority of jurisdictions, an appeal reviews whether the assessor's value is supportable and cannot be used to raise your assessment above the noticed value. Check your own state's rules, but the common asymmetry is a small fixed cost against a reduction that compounds for every year you own the home.

Who is most likely to be over-assessed?

Recent buyers, non-homesteaded owners, and owners of new construction, because assessment caps have not built up any cushion for them and the assessment tracks full market value. We measured this directly in Florida: across 8.29 million residential parcels, 28.4% (about 2.35 million homes) carry no meaningful cap protection, and they pay tax on full market value while long-held identical homes nearby are assessed at a fraction of it. Owners of homes with condition problems the county cannot see, and owners in neighborhoods with mixed housing stock where mass appraisal models perform worst, are also over-represented.

Does appealing my property taxes actually work?

Appeals succeed at meaningful rates when they are supported by evidence, and fail routinely when they are not. The deciding factor is almost never how unfair the increase feels. It is whether you bring specific comparable properties, a documented factual error, or a recent arm's length sale price. Assessors and review boards are evaluating a number against evidence. An appeal with a comp table and a property card correction is a different proceeding from an appeal with a complaint about the tax rate, which is not appealable anywhere.

Find your deadline before you do anything else

This is the one step with no recovery. Appeal windows are short, they vary enormously, and they are strictly enforced.

• Texas: generally May 15, or 30 days after your notice was mailed, whichever is later
• Florida: 25 days after the TRIM notice mails, usually landing in mid-September
• Georgia: 45 days from the date on the annual notice of assessment
• New Jersey: April 1 in most municipalities, January 15 in some
• Pennsylvania: commonly September 1 for the following tax year, with county variation
• Illinois: no statewide date, filed township by township as each is reassessed
• Colorado: a spring protest window set by statute

Confirm yours on your state's guide and put it in your calendar before you start gathering evidence. A perfect case filed one day late is worth exactly nothing.

Run the check

Twenty minutes and free public data will tell you whether you are one of the roughly one in five. Start with Test 1 if you bought recently, Test 3 if you did not, and do Test 2 either way, because it is the one that produces evidence you can actually file.

If you would rather have the comparison built for you, that is what we do. AppealMyTax finds your parcel in real county records, runs the uniformity comparison, and shows you the result before you pay anything. That is deliberate: you should be able to see whether you have a case before you decide whether it is worth $49 to us.

If there is a case, the $49 report delivers the comparable properties, the value gap, and the supporting evidence as a filing-ready PDF. One flat fee, never a percentage of your savings, and you keep every dollar you win. If you are fairly assessed, you learned that for free and you should not buy anything.

Check whether your house is over-assessed →

This guide is general information, not legal or tax advice. Assessment rules, caps, and deadlines vary by state and county and change over time. Verify your own jurisdiction's rules and dates with your assessor before filing.

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