Home Values Fell 1.7%. Tax Bills Rose 3%. Fewer Than 5% of Owners Bothered to Appeal.

Last year the average American single-family home lost value and got a bigger tax bill anyway.

ATTOM's annual property tax analysis, published April 9, 2026 and covering tax year 2025, found the average single-family home was worth $494,231, down 1.7% from the prior year, and generated $4,427 in property taxes, up 3%. The effective tax rate climbed from 0.86% to 0.90%, the highest reading since 2020.

Every investor I talk to is obsessed with the rate on their debt. Almost none of them can tell me what their assessed value is.

That's backwards. Your mortgage rate gets fixed once, at a closing table, and then it stops mattering. Your property tax bill reprices every single year, it moves in one direction, and it comes out of net operating income before you ever see a dollar.

The gap is widening right now. The Census Bureau's Quarterly Summary of State and Local Tax Revenue, released September 10, shows state and local governments collected $212.3 billion in property taxes in the second quarter of 2026 on a seasonally adjusted basis, up 4.0% from the same quarter a year earlier. Over the same stretch, the median existing-home price rose 1.6%, according to the National Association of Realtors' August existing-home sales release.

Governments grew their take two and a half times faster than the asset it's levied on.

The Assessor Is Underwriting a Market That Already Turned

Assessment is a lagging function. Your county sets a valuation date, pulls sales that closed before it, and mails you a notice months later. The number on that notice describes a market that has already moved, and in 2026 it's moved in the direction that helps you.

That same NAR release put August existing-home sales at a seasonally adjusted annual rate of 3.98 million, down 2.0% on the month and 1.2% from a year earlier, with inventory at 1.62 million units and supply at 4.9 months. That's the highest supply reading in more than a decade, and the first inventory print above 1.6 million since November 2019. NAR chief economist Lawrence Yun called it "a mild dip in home buying activity due to high mortgage rates."

Nearly five months of supply means sellers are cutting. It means the comps closing today sit below the comps that closed when your assessor set the valuation date. That spread isn't an opinion you have to argue.

It's a stack of closed sales you can put in a folder.

And almost nobody does it. The National Taxpayers Union Foundation estimates that "between 30 and 60 percent of taxable property in the United States is over-assessed," while "typically fewer than 5 percent of taxpayers challenge their assessments." Most owners who do file and come prepared, the Foundation says, win at least a partial reduction.

Up to six in ten properties are carrying an inflated bill, and fewer than one in twenty owners files a single piece of paper about it.

I'll be honest about the edge of what I know here: nobody publishes how many of that 30-to-60% are over-assessed by enough to be worth an afternoon of your time. The NTU range tells you the odds are good. It doesn't tell you the size of the prize on your specific parcel, and only your comps can.

Collections Up 4%, Values Down 1.7%

The single number that matters most in the ATTOM data is the effective rate, which moved from 0.86% to 0.90%. That's a 4.7% jump in the rate itself, independent of any change in value, and it's the mechanism by which your bill rises in a year your property is worth less. The breadth matters too: 111 of the 221 metro areas ATTOM analyzed saw bills rise faster than the 3% national average, which makes this a national repricing rather than a few bad counties.

The rest of the picture, from ATTOM and the Census collections table:

• $396.8 billion in property taxes levied on 89.6 million single-family homes, up 3.7% year over year.
• $4,427 average bill, up 3%, against an average home value of $494,231, down 1.7%.
• Memphis bills rose 34%, the sharpest move among large metros.
• Illinois carries the highest state effective rate at 1.84%, followed by New Jersey at 1.58%. New Jersey's average bill of $10,499 runs nearly ten times West Virginia's $1,081.
• Among metros above one million people, Rochester, New York sits at 1.82% and Phoenix at 0.39%, close to a fivefold spread on identical dollars of value.
• Property taxes made up 36.7% of all state and local tax revenue in Q2 2026, the single largest category. Unadjusted year to date, collections run $422.8 billion against $407.7 billion in 2025, a 3.7% gain; the 4.0% figure above is the seasonally adjusted second-quarter comparison, which strips out the lumpy winter billing cycle.

Now run it against your own book. Take one rental carrying the national average $4,427 bill. A 12% assessed-value reduction saves $531 a year in net operating income, and at a 6.5% cap rate that's roughly $8,170 of enterprise value created by an afternoon of comp pulling, right up until the next reassessment resets the clock.

Ten doors turns that into $5,300 a year and better than $81,000 of value. There isn't a deal in your pipeline with that hourly rate.

Common Mistakes Investors Make Here

• Arguing the tax rate instead of the assessed value. Taxing bodies set the rate and you can't appeal it. The value is an opinion written by someone who has never been inside your property. Attack the opinion.
• Using the wrong comps. Sales after the valuation date are irrelevant, and so are renovated flips two streets over. You need arm's-length sales of similar properties that closed inside the assessor's window, with condition differences noted explicitly.
• Citing your own purchase price when it hurts. If you bought above the assessment, don't volunteer it. If you bought below it, that's often your single strongest exhibit.
• Missing the window. Most jurisdictions give 30 to 45 days from the notice date and the deadline is hard. A perfect case filed on day 46 is worth nothing.
• Leading with hardship. Boards don't care that rates are high or that your insurance renewed badly. They rule on value. Bring comps, dated photos of deferred condition, and the property record card.

Where I Land

Property tax is the most mispriced line item on an American investor's P&L, and the industry treats it like weather. I think that's indefensible. I'd rather spend one Saturday filing three appeals than spend a month hunting a new acquisition, because prepared appeals win more often than they lose in a field where fewer than 5% of owners file at all, they cost nothing in most counties, and the savings run straight into the terminal value of every property I own.

Here's my called shot. When ATTOM publishes its next annual analysis in April 2027, the national effective tax rate will print above 0.92%. Collections are compounding at 4% against a price index growing 1.6%, and nothing in the September data bends either number this year. Municipalities don't cut levies when values soften; they raise the rate to hold revenue flat.

Which raises the fair objection: if the county just re-rates to hold revenue flat, what did my appeal actually buy me? A smaller slice of a levy that was going to be collected either way. Property tax is close to a zero-sum split of a fixed number, and every owner who doesn't file is quietly covering the difference for the ones who do. That's not a reason to skip the filing. It's the reason the 5% keeps winning.

So I'd file on every property whose assessed value sits above its realistic 2026 sale price, every year, without exception, and I'd put it in the operating calendar rather than treat it as a special project. The people telling you to wait for rate relief are pointing you at the one number you've already locked in.

The number you can still move is the one you've been ignoring.

How to Use PropGPT for This

Every appeal comes down to one question: what did comparable properties actually sell for, before your assessor's valuation date? That's a data problem, and it's exactly what PropGPT sits on top of. Swap your own address and ZIP into each of these.

"Pull all arm's-length single-family sales within 0.5 miles of [your property address] that closed between January 1 and December 31, 2025, with 3 bedrooms, 2 baths, and 1,400 to 1,900 square feet. Show sale date, sale price, price per square foot, square footage, year built, and lot size, sorted by price per square foot."

This builds your comp exhibit. Constrain the date range to the assessor's valuation window rather than to today, or the board will throw it out.

"Here are the addresses of the 9 properties I own: [paste list]. For each one, compare the current assessed value to the median sale price of comparable properties sold in the last 12 months within a half mile, and rank them by the dollar gap between assessment and market."

Portfolio triage. Appeal the widest gaps first, because you have limited Saturdays and a 3% overassessment isn't worth the filing.

"What is the assessed value, last sale date, last sale price, square footage, bedroom and bath count, year built, and lot size on record for [your property address]?"

Run this against the property record card you request from the assessor. Square footage and bath-count errors are the most common defects on file, and a factual correction is a far easier win than a valuation argument.

"Show me the median sale price by quarter for 3-bedroom single-family homes in ZIP [your ZIP] for the last eight quarters, with the count of sales in each quarter."

This is your market-trend exhibit, the chart showing prices peaked before the valuation date and have softened since.

"List single-family sales within one mile of [your property address] in the last 12 months under $200,000, and show the sale type or deed type recorded on each."

Assessors usually exclude distressed sales from their models, but those sales often set the real floor on a street. Knowing where they closed tells you whether that exclusion is defensible or is quietly holding your value up.

The Bottom Line

The door to knock on is your county assessor or the equivalent board of review, and the process is public. In Illinois, that's the Cook County Board of Review, which publishes township-by-township filing windows. In Texas, the Comptroller's property tax protest page lays out the appraisal review board process and the statutory deadlines.

Find the equivalent page for your county, note the notice date and the filing deadline, and request your property record card. That single document lists every physical characteristic the assessor believes your property has, and it's where the cheapest wins hide. Bring comparable closed sales from the valuation window, dated photos of any condition issues, and the corrected characteristics. Most jurisdictions charge nothing to file.

This is reporting, not legal or tax advice, and appeal rules vary sharply by state and county. Confirm your own deadlines with your assessor before you rely on anything here.

Pull your comps this week, while the gap is still on your side of the table.