Learn exactly how to find comparable properties for a property tax appeal using a proven method. Pick 3–5 defensible closed sales from your own neighborhood, rank them by similarity, and present a clean comp packet that speaks the assessor’s language.
# How to Find Comparable Properties for Tax Appeals: A Practical, Defensible Method
If you’re trying to figure out how to find comparable properties for tax appeal purposes, you’re already doing the right thing. In most counties, the strongest property tax appeals are the boring ones: a clean set of truly similar recent sales (“comps”), presented clearly, showing your assessment is above what the market supports.
The hard part isn’t finding addresses. It’s picking comps that an assessor (or appeals board) will agree are legitimately comparable—and then explaining those comps in a way that makes your conclusion hard to ignore.
This guide gives you a repeatable method you can use anywhere in the U.S., plus practical rules of thumb on how many comps you need, where to find them, and how to handle differences like upgrades, basements, lots, and condition.
Most residential values are built (directly or indirectly) from the market using a sales comparison approach—meaning: look at recent sales of similar homes and infer value. Counties often do this at scale (mass appraisal), using models and “comparable sales algorithms” to value thousands of properties efficiently. That’s why a well-chosen comp set is so persuasive: you’re speaking the assessor’s language. See the IAAO’s discussion of mass appraisal and comparable-sales modeling in its Standard on Mass Appraisal of Real Property and appeal evidence guidance in its Standard on Assessment Appeal.
One important mindset shift: your goal isn’t to prove your home is “worth less than last year.” Your goal is to show that as of the county’s valuation date, similar homes sold for less than the county’s value conclusion for your home.
A good comp is similar in the ways that actually drive price, and different only in ways you can explain. Here’s the hierarchy most assessors (and appraisers) expect.
Start with the tightest location match you can:
Cross-neighborhood comps are where most DIY appeals fall apart. If you use a comp outside your neighborhood, you should be able to explain why it’s still the same market (same buyer pool, similar lot sizes, similar age and build quality, similar price bracket).
Sale date matters because markets move.
Professional guidance on what counts as a comparable sale (and why sale verification matters) is summarized in IAAO materials, including its definition of “Comparable Sales” in the IAAO Glossary.
Match the broad category first:
If your home is a townhome in a community with both interior and end units, that “unit position” can be as important as bedroom count.
Size isn’t just square footage—it’s how the home lives.
You can often defend small differences in square footage, but it’s harder to defend a comp that is a totally different layout category.
Counties frequently assume “average condition” unless they have data that suggests otherwise. If your home is dated, has deferred maintenance, has a roof/HVAC near end of life, or has foundational/moisture issues, that’s a comp selection issue and an evidence issue. You should try to use comps that reflect similar condition (or be prepared to explain why your home should be valued lower than a renovated comp).
Lot premiums are real, especially when they change usability or privacy:
If you ignore lot/site differences, your comp set will often look “too high” or “too low” and the assessor will dismiss it.
You can build a credible comp set from public sources, but not all sources carry equal weight in an appeal.
This is the gold standard because it’s the county’s own ecosystem:
Many counties include a “sales search” tool or show recent sales directly on parcel pages. If your county provides sale data and characteristics in a single place, use it—because it’s the most defensible record in a hearing.
Recorded deed data can help verify the transaction date, whether it was a standard sale, and whether there were multiple parcels involved. This is especially useful when a sale price looks “off” and you need to confirm whether it’s a transfer you should exclude.
MLS is often the best for condition and feature detail (photos, upgrades, concessions), but many homeowners can’t access it directly. If you have a friendly agent willing to print MLS sheets, those can be powerful supporting exhibits—especially to document renovations/condition differences.
Sites that estimate values can be helpful for lead generation (finding candidate comps), but they’re rarely the best “final exhibit” in an appeal because estimated values are not the legal standard in most jurisdictions, data can be stale or incomplete, and they may not show what the county recognizes as the official record.
Use them to discover potential comps—then verify everything against county records.
There’s no universal rule, but most strong DIY appeal packets follow a simple pattern:
Why not 10–15 comps? Because volume looks like you’re “throwing spaghetti.” A small set of tightly matched comps is easier to defend, easier to understand, and harder to dismiss.
This is the process we recommend (and it mirrors how mass appraisal systems narrow candidates before ranking them).
Before you pick a comp, you need to know what you’re arguing:
Many appeal systems are designed around valuation evidence and the kind of documentation described in the IAAO’s homeowner-facing guide, Understanding Your Assessment.
Use the smallest “market area” that produces enough recent sales:
If you have plenty of sales in your subdivision, don’t leave it. The moment you cross into a different micro-market, your comp set becomes easier to attack.
From the county site (or public sales data), pull a list of candidate sales that meet broad filters:
Don’t worry about perfection yet. You’re just building the pool you’ll rank.
Exclude candidates that will weaken your case:
IAAO emphasizes the importance of verified, usable sales data in valuation modeling and appeals; see its Standard on Verification and Adjustment of Sales and broader standards list in the Guide to Assessment Standards.
This is where most homeowners can level up quickly. Instead of picking comps based on gut feel, rank them using a consistent scoring method.
A simple scoring model (0–100) can look like this:
Pick your top 3–5 by score, then sanity-check: Would a buyer choose between these homes and mine?
For each comp, capture:
This part scares people, and it shouldn’t—because you don’t need to run a full appraisal to make a clear argument. You need to be consistent, modest, and market-based.
Professional guidance on adjustments in the sales comparison approach generally focuses on market-derived elements of comparison and reasoned adjustments (not random “I think it’s worth $20k less” statements). See, for example, state regulator practice guidance describing adjustments in the sales comparison process: Colorado real estate appraiser practice guidance. Fannie Mae’s appraisal guidance also describes the sales comparison analysis structure and the role of comparable sales selection: Sales Comparison Approach section.
Use adjustments only when:
1) The difference is obvious and meaningful to buyers, and 2) You can explain the direction clearly, and 3) You keep it conservative.
Common differences you can usually address in plain language:
Pick one of these approaches and stick to it:
1) Paired sales logic (best, if you have it): If two similar homes sold around the same time and the key difference is one feature (e.g., finished basement), you can infer a reasonable adjustment range.
2) Local price-per-square-foot (use carefully): If your comps are very similar and your market trades somewhat consistently on a per-square-foot basis, you can use it as a check, not as the entire method. Avoid applying PPSF across wildly different sizes or different neighborhoods.
3) “Condition narrative” instead of precise dollars (often enough): In many informal reviews, a strong narrative plus photos/repair estimates can move value without you putting a dollar on every issue.
If you find yourself doing heavy adjustments, that’s usually your cue to go back and find better comps.
Even great comps can lose if they’re presented poorly. Your goal is to make the reviewer’s job easy.
1) One-page summary (the “case cover sheet”)
2) A clean comp grid (3–5 comps)
Include:
3) A map view
A simple map screenshot showing your home and comps builds credibility fast.
4) Exhibits for each comp
County record printout + (if available) listing photos or MLS sheet.
IAAO’s homeowner guidance explicitly points to comparable-property evidence as a core ingredient in effective appeals. See Understanding Your Assessment.
Keep “Key Notes” short and factual. If you need a paragraph, put it on the exhibit page, not in the grid.
You’re not trying to “win an argument.” You’re trying to show a clean, supportable conclusion.
Let’s say your home is a 2,200 sq ft, 1998-built, 4/2.5 in a suburban subdivision. The county value implies $260/sq ft, but recent neighborhood sales feel lower.
A strong comp search would look like:
1) Pull all closed sales in your subdivision for the last 6–12 months. If you get 5–15 sales, you’re in a great place.
2) Filter to:
3) Exclude:
4) Pick the top 3–5 that most resemble:
Then you present:
That package is easy for a reviewer to accept (even if they don’t agree with every detail).
If you want to describe your approach like a pro (or if you’re building this into a workflow), here’s the simplest explanation of a comps-selection engine:
1) Define the subject property’s “value drivers”: location market area, property type, living area, year built, lot/site, condition proxy, key features.
2) Pull a broad set of recent sales candidates: public sales records within the market area around the valuation date.
3) Remove sales that are not usable: non-market transfers, distress, outliers, mismatched property types, new build premiums that don’t match the subject, etc.
4) Score each candidate by similarity: heavier weight on location and size; moderate on time and age; additional weight on lot/site and functional features.
5) Select a compact set that is easy to defend: usually 3–5 core comps + backups.
6) Produce a presentation-ready packet: a one-page summary, comp grid, map, and exhibits.
If you want the professional view of how comparable selection fits into automated valuation and mass appraisal, the Appraisal Foundation’s advisory is a useful reference point: Valuation Advisory #5: Identifying Comparable Properties in Automated Valuation Models for Mass Appraisal.
Comparable sales are the backbone of most successful residential tax appeals because they directly connect your home’s value to what similar homes actually sold for. The strongest approach is systematic: define your market area, build a candidate pool, exclude unusable sales, rank candidates by similarity, and present a compact set of 3–5 defensible comps with clean exhibits.
If you keep your comps close in location, similar in size and type, reasonable in timing relative to your valuation date, and honest about condition and lot differences, you’ll end up with an argument that feels professional—without needing to be a tax expert. From there, the next step is packaging your comps into a simple narrative and evidence layout that your assessor (or board) can absorb quickly and verify.