Every spring, county assessors mail out a new valuation notice, and most homeowners just pay the bill without looking at it. Yet data from the National Taxpayers Union and state-level appeal boards shows that roughly 60%–70% of homeowners who formally appeal their assessment win some kind of reduction — often $500 to $2,000 per year, and sometimes far more on high-value homes. The hard part is knowing whether your specific situation is worth the filing fee, the appraisal cost, and the afternoon of paperwork.
This property tax appeal calculator does that math for you. It compares the value your county has assigned to your home against what you believe it is actually worth on the open market, multiplies the gap by your local tax rate, and then subtracts the cost of appealing so you can see the real dollar payoff — including your first-year return on investment and how long it takes to break even.
How to Use
- Enter the County Assessed Value shown on your latest property tax bill or assessment notice. This is the number the county is currently taxing you on.
- Enter your Estimated Market Value based on recent comparable sales in your neighborhood. Pull three to five homes that sold in the last six months within a half-mile of yours, with similar square footage, bed/bath count, and condition, and use the average sale price. Zillow's Zestimate, Redfin, and your county's own appraisal district portal are good starting points.
- Type your Effective Property Tax Rate as a percentage. If your bill shows mills (for example, 12.0 mils), divide by 1,000 to get 1.2%. This rate usually combines county, school district, city, and special-levy millage.
- Enter your Appeal Cost. A do-it-yourself appeal often costs only the filing fee (often $0–$50). Hiring a licensed property tax consultant or a real-estate attorney typically runs $300–$1,000, sometimes charged as a percentage of the first-year savings.
- Set Years You Plan to Own the home. A successful appeal lowers your bill every year until the next reassessment, so a five-year holding horizon usually makes even a small reduction worthwhile.
The result card shows how much you are over-assessed, your current versus projected annual tax bill, the annual savings if you win, the net cash result after year one, the total net savings over your planned ownership period, and your first-year ROI.
The Math Behind an Appeal
Property tax is an ad valorem tax — it is a percentage of the value the government assigns to your home. The core formula is simple:
Annual Tax = Assessed Value × Effective Tax Rate
An appeal does not change the tax rate. It only challenges the assessed value number. If you win, the county lowers that number, and your tax bill drops proportionally. The potential annual savings is therefore:
Annual Savings = (Assessed Value − Market Value) × Tax Rate
Worked example on a home assessed at $400,000 with comps showing a true market value of $350,000, in a county with a 1.2% rate: the over-assessment is $50,000, and multiplying by 1.2% gives $600 per year in potential savings. If the appeal costs $500 (a filing fee plus a $400 independent appraisal), your first-year net is $600 − $500 = $100, but over five years you keep $600 × 5 − $500 = $2,500. The first-year ROI on the $500 investment is $600 / $500 = 120% — a return very few other household expenses can match.
If the market value you entered is higher than the assessed value, the calculator reports a negative over-assessment. That means the county is already taxing you below market, and an appeal would almost certainly raise your bill rather than lower it — do not file in that situation.
When an Appeal Is Worth It
Appeals are most attractive when:
- Your assessment jumped much faster than neighbors'. If your bill went up 15% while similar homes on your block went up 3%, that asymmetry is your strongest evidence.
- Recent comps are clearly below your assessed value. The assessor's own market study is the standard; if three or more nearby sales support a lower number, the appraisal review board tends to agree.
- You have owned the home for several years and plan to stay. A successful reduction compounds: it applies next year, the year after, and every year you keep the home.
- The annual savings is at least 2–3 times the appeal cost. If an attorney wants $1,500 to fight a $300/year bill, it is a bad trade unless you expect the reduction to hold for a decade.
Appeals are usually not worth it when the gap between assessed and market value is small (under 5% of assessed value), when your home actually sold for more than the assessed value recently, or when state law caps assessment growth (for example, California's Proposition 13 or Florida's Save Our Homes) in a way that already locks in a below-market number.
Examples
Example 1 — The default case that pays back in under a year. A homeowner in Texas opens their bill and sees a $400,000 assessed value, but recent sales of three nearly identical homes on the same street closed at $350,000. The effective tax rate is 1.2%, and they budget $500 for a filing fee plus a residential appraisal. The calculator shows a $50,000 over-assessment, $600/year savings, a $100 net in year one, and a 120% first-year ROI. Over the planned five years in the home, the net gain is $2,500.
Example 2 — A high-value home in a high-tax state. A $1,500,000 home in New Jersey is assessed at $1,500,000 but comps support $1,200,000. At a 2.5% effective rate, the over-assessment is $300,000 and annual savings are $7,500. Even with a $2,000 lawyer/appraisal cost, the first-year net is $5,500 and the 10-year net is $73,000 — a textbook case to appeal.
Example 3 — No gap, no appeal. A $350,000 home is assessed at exactly $350,000. The calculator shows $0 over-assessment and $0 savings, and warns that filing would likely be a waste of the $500 cost. The right move here is to wait for the next reassessment cycle and re-check comps then.
FAQ
How much can I save by appealing my property taxes?
The savings equals the gap between your county's assessed value and the true market value (supported by comps), multiplied by your effective tax rate. On a typical $400,000 home assessed $50,000 above comparable sales at a 1.2% rate, that is about $600 per year, or $3,000 over five years. High-value homes in high-tax states can save $5,000–$10,000 per year.
Is it worth paying someone to appeal my property taxes?
It depends on the size of the gap versus the fee. A useful rule of thumb: if the projected annual savings is at least two to three times the consultant's or attorney's fee, hire a professional. If the savings is under $300/year, the filing fee and a free county board hearing are usually enough. Many firms work on contingency (taking 30%–50% of the first-year savings), which aligns their incentive with yours.
What is the success rate of property tax appeals?
State-level appraisal board data consistently shows that roughly 60%–70% of homeowners who present solid comparable-sale evidence win some reduction. Success is much lower when the appeal relies only on "my taxes are too high" without comps, photos, or evidence of defects (bad roof, outdated plumbing, flooding). Bringing three to five recent nearby sales at or below your target value is the single biggest predictor of winning.
How long does a property tax appeal take?
Most informal review hearings resolve in 30–90 days. Formal appeals to a county board can take 3–6 months, and appeals to state court take 1–2 years. The good news: most jurisdictions apply any approved reduction retroactively to the current tax year, so you get a refund check or credit even if the hearing drags on.
Can I appeal every year?
In most states you can file an appeal every reassessment cycle, but you should only do so when the assessed value is clearly out of line with market comps. Filing a losing appeal repeatedly trains the appraisal board to dismiss your case, and in some counties repeated appeals trigger a more careful inspection that can actually raise other homes in the neighborhood.
What counts as good evidence for an appeal?
The strongest evidence is three to five recent arm's-length sales of similar homes within a half-mile, ideally within the last six months. Supplement with photos of your home's condition, a floor-plan comparison, and — if you can afford one — an independent residential appraisal from a state-licensed appraiser. The county's own appraisal worksheet is also public record and often contains factual errors (wrong square footage, wrong number of bathrooms) that are free wins.
Disclaimer
This property tax appeal calculator is provided for informational purposes only and does not constitute legal, tax, appraisal, or financial advice. Savings estimates are based on the inputs you enter and the simple ad-valorem tax formula; actual appeal outcomes depend on your county's appraisal board, local law, the quality of your evidence, and whether you win a reduction. Tax rates, exemptions, homestead caps, and appeal deadlines vary by state and county. Always confirm your assessment details, filing deadlines, and procedural rules directly with your county assessor's office, and consider consulting a licensed property tax consultant or real-estate attorney before filing a formal appeal.