Estimates of how many American homes are assessed above their true market value run startlingly high — by several measures approaching half of all properties. What almost never follows is the obvious response: only about one in twenty owners ever challenges the number that sets the tax bill. That gap is quietly expensive, because an assessment is not a fixed fact but an opinion of value, and opinions can be contested. A documented appeal can shave hundreds, and sometimes thousands, of dollars off an annual property-tax bill that will otherwise be paid in full, year after year.
Why so many assessments run high
Local assessors rarely walk through each home. Most rely on mass appraisal, modeling values across whole neighborhoods from sales data, square footage, and property records that can be years out of date. That approach scales, but it also builds in error. A home carrying the wrong square footage, an extra bathroom it does not have, or a finished basement that was never finished can be taxed on a value it never possessed. In a cooling market, assessments can also lag behind falling prices, leaving owners billed on a peak that has already passed.
The scale of the problem is where the case for appealing begins. The National Taxpayers Union Foundation estimates that somewhere between a third and 60 percent of U.S. properties are over-assessed, a range whose midpoint sits close to half of all homes. CBS News reporting on the issue notes that despite those odds, only about 5 percent of owners appeal, leaving the vast majority to pay a bill built on a value no one has verified against the current market.
For older homeowners, the stakes compound. A retiree who stays in the same house for a decade pays an inflated assessment ten times over if it goes unchallenged, and property taxes are one of the few major retirement costs that rarely fall on their own. Correcting the base value once can lower every bill that follows until the next reassessment.
Free retirement updates: One number can cost or save hundreds a month in retirement. The free Retirement Shield newsletter surfaces the ones worth knowing. Sign up free.
What evidence actually wins an appeal
An appeal succeeds or fails on documentation, not on how high the bill feels. The strongest case is a set of comparable recent sales — similar homes nearby that sold for less than the assessed value — which directly undercut the assessor’s estimate of what the property is worth. Errors in the official property record are equally powerful: a corrected square footage, an amended room count, or proof that a listed feature does not exist can force a lower number without any argument about the market at all.
Condition matters too. Photographs of a failing roof, foundation cracks, or outdated systems document why a home is worth less than the model assumes, and appraisals or contractor estimates can reinforce the point. CBS News guidance on the process stresses that a well-supported appeal is far more likely to succeed than a bare complaint, because the review board is weighing evidence against the assessor’s data rather than reacting to frustration.
The cost of trying is usually low. Many jurisdictions charge nothing to file an appeal, and a homeowner can often assemble the comparable sales and record corrections without hiring anyone. That math — little to lose, potentially hundreds a year to gain — is what makes the 5 percent participation rate so striking.
Preparation is where the effort concentrates. Pulling three to five genuinely comparable sales, checking the property record for the home’s listed dimensions, and photographing any real defects can usually be done in an afternoon, and many assessor offices post the underlying data online. The review board is not looking for eloquence; it is looking for a credible number backed by evidence it can verify, a standard an ordinary homeowner can meet without professional help.
The short window that decides the outcome
Timing is the trap that catches most owners. Appeal rights are tied to the assessment notice, and the window to file is often measured in weeks, not months. A homeowner who sets the notice aside, assuming the value is simply official, can lose the entire year’s chance to contest it and be forced to wait until the next cycle. The deadline, not the merits, ends most potential appeals before they begin.
Missing that window carries a cost beyond a single bill. Because an assessment usually rolls forward until the next reassessment, an uncorrected error keeps overcharging a household every year in between. CBS News coverage of the appeals process describes homeowners who cut their bills substantially by acting within the window, precisely because a lower base value keeps paying off long after the paperwork is filed.
The larger puzzle is why a process this cheap and this winnable stays so rarely used. Part of the answer is that assessments arrive wrapped in the authority of an official document, and few owners think to question a government number. For a retiree weighing whether the effort is worth it, the relevant figure is not the appeal’s difficulty but the odds: with over-assessment estimated near half of all homes and only a sliver of owners ever pushing back, the untested bill is often the expensive one.
This article was produced with AI assistance and reviewed against primary sources by The Money Overview editorial team.
More Financial Reading
