Why Comps Decide Appeals
Assessment review boards see two kinds of homeowners: the one who says "my taxes are too high," and the one who hands over a page showing five similar homes nearby assessed or sold for less. The first gets sympathy; the second gets a reduction. Your opinion of your home's value carries no evidentiary weight, comparable properties do.
There are two distinct kinds of comps, and knowing which game you're playing matters:
- Sales comps argue your assessed value exceeds your home's market value, using recent sold prices of similar homes.
- Equity (uniformity) comps argue you're assessed higher than similar homes are assessed, regardless of market value, using the assessor's own records.
What Makes a Comp Valid
Boards apply informal but consistent screens. A comp survives scrutiny when it matches your property on the dimensions that drive value:
| Factor | Rule of thumb |
|---|---|
| Sale date | Within 12 months of the valuation date, closer is stronger. Most states assess as of January 1, so sales from the back half of the prior year are gold |
| Location | Same neighborhood or subdivision, ideally within half a mile, and the same school district. Crossing a district line weakens a comp badly |
| Size | Living area within 10-20% of yours (a 2,000 sq ft home: comps from ~1,600 to 2,400) |
| Age & type | Built within roughly 10-15 years of yours, same style (don't comp a ranch against a colonial) |
| Sale type | Arm's-length only: no foreclosures, short sales, estate sales, or transfers between relatives, boards discard them |
Aim for three to five comps. One comp looks cherry-picked; ten look like you didn't screen. And expect the assessor to bring their own comps: pull the highest-value ones a reasonable person might use against you and be ready to explain why yours are more similar.
Where to Find Comp Data (Free)
- Your county assessor's own portal. The best source, because the board can't dispute its own data. Most counties let you search assessments, characteristics, and sales by street or neighborhood. This is also the only source you need for equity comps.
- Zillow and Redfin "sold" filters. Use actual sold prices only, never Zestimates or estimates, boards openly discount algorithmic values. Redfin often shows fuller history (list price, days on market, price cuts), which helps explain a low sale.
- A real estate agent. Agents can pull an MLS comp report in minutes and often will, free, for a past or hoped-for client. MLS data is the most complete and boards know it.
- County deed records for confirmed sale prices, though note that non-disclosure states (Texas among them) don't publish prices, there, MLS access or the appraisal district's own evidence matters more.
- In Texas specifically: request the appraisal district's evidence packet before your hearing, they must share the data they'll use, including their comps, and their own comps frequently support a reduction once adjusted properly.
Adjustments: Comparing Apples to Slightly Different Apples
No comp is identical, so you adjust the comp's price toward your property: if the comp has something better than yours, subtract value; if worse, add. The direction trips people up constantly, adjust the comp, not your home.
Example: your target is a 2,000 sq ft home with a 2-car garage. A comp sold for $415,000 with 2,200 sq ft (200 more than yours) and a 3-car garage. At an illustrative $150/sq ft for extra space, subtract $30,000; for the extra garage bay, subtract, say, $8,000. Adjusted value: about $377,000. Do this arithmetic on paper for each comp and present a simple table with the adjusted values and their median.
Two honesty rules that build credibility with boards: use modest, defensible adjustment figures for your market (per-square-foot rates and bathroom/garage values vary hugely by area, there is no national schedule), and adjust in both directions. A homeowner who only makes adjustments that lower the number gets discounted; one who shows a comp adjusting upward gets believed.
The Equity Play: When Sales Are Against You
Suppose recent sales in your neighborhood actually support the assessor's number, but the identical house two doors down is assessed 15% lower. That's an equity appeal: assessments are legally required to be uniform in most states, and your evidence is the assessment roll itself, not sales.
Pull the assessor's records for 5-10 genuinely similar homes and compute each one's assessment per square foot. If yours sits well above the median, you have a case even in a rising market. This is especially powerful in Texas, where the law says your protest must be granted unless the district proves your value is at or below the median of comparable, appropriately adjusted properties, putting the burden on them, and in Illinois, where uniformity is a state constitutional right and Cook County's uneven assessments make such comparisons fertile ground.
Presenting the Package
- One page per comp: photo, address, sale date and price (or assessment), key characteristics, your adjustments, adjusted value
- A summary table with the median adjusted value, and the number you're asking for (ask for a specific value, not "lower")
- A map showing your home and the comps, proximity is persuasive at a glance
- Bring your assessment record card too: if the county has your square footage or bath count wrong, that error compounds every comp comparison in your favor
Bottom Line
Three to five recent, nearby, arm's-length comps, honestly adjusted and cleanly presented, are the difference between an opinion and a case. Start from the county's own data, choose the sales-comp or equity-comp route based on which evidence favors you, and ask for a specific number. For the procedural side, deadlines, forms, hearings, see our step-by-step appeal guide and deadline calendar; and if the stakes justify it, here's when hiring a pro makes sense.