Comps are the whole case. Almost every property tax appeal that wins does it by putting comparable homes on the table and showing the assessor's number is out of line with them. So the work is not "find some cheaper houses nearby." It is find homes so close to yours that the assessor can't explain away the gap. Here is how to do that, where the data lives, and the traps that sink otherwise-decent appeals.
What makes a comp actually comparable
A comp is a home similar enough to yours that its value tells you something real about yours. Boards and assessors weigh a handful of features, roughly in this order of importance:
- Location. Same neighborhood or market area, ideally the same subdivision or a few blocks over. A home a mile away in a different school zone or across a highway is not comparable, no matter how similar the house.
- Living area. Similar finished square footage. Stay within roughly 10–15% of your home's size if you can. Value per square foot is how most of this argument gets made, so a big size gap poisons the comparison.
- Age and style. Built in a similar era, same basic type: a 1998 two-story colonial compares to another 1998 two-story colonial, not to a 1962 ranch.
- Lot and site. Similar lot size and situation. A half-acre corner lot and a quarter-acre interior lot are not the same, and a busy road, backing onto commercial, or a flood-prone position all move value.
- Condition and features. Similar bed/bath count, garage, basement, and general condition. A recently-gutted flip is not a comp for an original-condition home.
- Recency. For a sale-based comp, recent matters: within the last 12 months is ideal, and many jurisdictions want sales close to the assessment date you're challenging. For an assessment-based comp, the current assessed value on the roll is the point.
The test to apply to every candidate: if the assessor looked at this home next to yours, what would they say is different? If the honest answer is "not much," it's a good comp. If you can already hear "well, that one's 400 square feet smaller and sold in a bad month," drop it.
The two arguments comps support
Comps are not one-size-fits-all, because there are two distinct ways to win, and they use comps differently.
Over-market-value. You argue the assessor's estimate of your home's market value is too high, full stop. Here you use recent sales of comparable homes: three to five arm's-length sales that closed below your assessed market value once you line up size and features. This is the classic "my house isn't worth what you say" case.
Unequal or non-uniform assessment. You argue that even if the market value is arguable, you're assessed higher than comparable homes around you, which violates the uniformity principle that similar properties should be assessed alike. Here you use assessed values of comparable homes from the roll, and you compare on a per-square-foot basis. If ten homes like yours are on the books at $150 per square foot and yours sits at $185, that gap is the argument, no sale required.
Where to get the data
Nearly all of it is public and free. Three sources cover most appeals:
- Your county assessor's online property search. This is the source of truth. Almost every county publishes a parcel lookup that shows, for any address, the assessed value, land and building breakdown, finished square footage, year built, lot size, bed/bath count, and often the last sale price and date. This is where you find comps and pull their assessed values and characteristics. Use the assessor's own square footage for your home and the comps, so you're arguing on their numbers, not a third-party site's.
- Recent sales records. For market-value comps you need actual closed sales. Many assessors show recent sales in the parcel record; where they don't, the county recorder or clerk's real-property records, or a real-estate portal, will show recent sale prices. Confirm the sale was arm's-length, an ordinary open-market sale, not a family transfer, foreclosure, or estate sale, which don't reflect market value.
- Your assessment notice. The notice the assessor mailed you lists the assessed value you're challenging, and often the market value they started from and the deadline to appeal. That's your baseline, and the number every comp is measured against.
A note on the free real-estate portals: their "Zestimate"-style figures are estimates, not evidence, and a board will treat them as such. Use portals to spot candidate homes and rough sale prices, then verify every figure against the assessor's record and the official sale record before you rely on it.
How many to use, and how to present them
Three to five comps is the sweet spot. Fewer than three reads as coincidence; more than five dilutes your best matches and hands the assessor more targets. Pick your strongest three to five and lead with the closest one.
Lay them out as a simple table the reader can scan in ten seconds, your home in the first row, comps below:
| Property | Sq ft | Year | Assessed value | Per sq ft |
|---|---|---|---|---|
| Subject (your home) | 2,000 | 1998 | $370,000 | $185 |
| Comp A — 2 blocks E | 2,050 | 1997 | $308,000 | $150 |
| Comp B — same street | 1,940 | 1999 | $296,000 | $153 |
| Comp C — same subdivision | 2,100 | 1998 | $325,000 | $155 |
Then say plainly what the table shows: comparable homes in the same area are assessed around $150–$155 per square foot, yours is at $185, and applying the neighborhood figure to your 2,000 square feet points to roughly $305,000–$310,000 rather than $370,000. Include the parcel numbers or addresses so the assessor can pull each one and verify it. Make it easy to check, and easy to agree with.
Where a comp differs from your home in a way that matters, don't hide it, adjust for it. If a comp has an extra bathroom or a finished basement yours lacks, acknowledge it and note it cuts the other way. A packet that quietly ignores obvious differences invites the assessor to make the adjustment for you, unfavorably.
The pitfalls that sink appeals
Most losing comp packets fail the same few ways:
- Cherry-picked comps. The big one. You find the three cheapest homes nearby, but they're cheap because they're smaller, older, in poor condition, or on a bad lot. The assessor names the difference and the comp evaporates. A low number is not a comp; a genuinely similar home that's still valued lower is.
- Distressed or non-arm's-length sales. Foreclosures, short sales, family transfers, and estate sales don't reflect open-market value, and most boards will exclude them. Confirm each sale was ordinary before you lean on it.
- Ignoring adjustments. Treating a comp with an extra 500 square feet or a pool as if it were identical. Compare like with like, or adjust and show your work.
- Mixing up the argument. Bringing sale prices to a uniformity argument, or assessed values to a market-value argument. Match the evidence to the claim you're making.
- Stale or wrong-date comps. Sales from three years ago, or after the valuation date your jurisdiction uses. Check what date your assessment is pegged to and stay near it.
One honest caveat: procedures, valuation dates, and which arguments a board will hear differ by jurisdiction, and this is general information, not legal or tax advice. Some states lean heavily on the uniformity argument; others weight recent sales. Your county assessor's site and your appeal instructions will tell you which comps they want and by when. Check your local appeal deadline first, because the best comp packet in the county is worth nothing if it lands a day late.
The short version
Pull three to five homes near yours that genuinely match on location, size, age, style, and condition, and are assessed lower per square foot (or sold lower, for a market-value case). Get the numbers from the county assessor's property search and the official sale record, not from an estimate. Compare on a per-square-foot basis, present it as a clean table with parcel numbers, and adjust honestly for any real differences. Don't cherry-pick a cheap house that's cheap for a reason, because that's the one thing the assessor is looking for.
Skip the parcel-by-parcel hunt.
The report pulls comparable properties near your address from the assessor's own records, ranks them by how closely they match, works out the per-square-foot gap, and assembles the comp table and evidence pack you'd otherwise build by hand.
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