How We Calculate Your Comparable Reference Value
Two methods, both anchored in the Texas Tax Code. Both built from public records you can verify yourself, comp by comp. Here’s the math, source by source — nothing held back.
The Two Statutory Paths
Sales approach — Tex. Tax Code §41.43(b)(1). The appraised value cannot exceed the property’s market value. Recent arms-length sales of comparable properties measure that market value directly.
Equity approach — Tex. Tax Code §42.26(a)(3). The appraised value cannot exceed the median of appraised values of a reasonable number of comparable properties, appropriately adjusted. This is the unequal-appraisal path, anchored in the appraisal district’s own records rather than market sales.
Both paths are independent grounds for relief. We build both because (a) sales evidence is sometimes unavailable in low-turnover neighborhoods and (b) panels weigh whichever evidence is stronger for a given property.
Where the Data Comes From
| Source | What we use it for |
|---|---|
| County ArcGIS (MCAD, HCAD, DCAD, TCAD) | Subject property record, neighborhood comp pool, lot/year/sqft attributes |
| TrueProdigy API | Subdivision-coded equity comps, appraisal history, taxable detail |
| Redfin sold listings (CSV download) | Recent sales comps, subject ZIP plus adjacent ZIPs |
| HAR.com listing photos | Subject and comp photo enrichment when public |
| FEMA NFHL flood maps | Flood-zone classification for condition rebuttal |
All sources are public records or commercially available data feeds. Nothing private is used.
How the Adjustments Work
Each comp is adjusted up or down so it’s an apples-to-apples comparison with your property:
Land-size adjustment. When the comp’s lot acreage differs from yours by more than 0.01 acre, we apply the appraisal district’s own per-acre rate (extracted from the subject’s land record):
Land Size Adj = (subject.acres − comp.acres) × subject.per_acre_rate
Square-footage adjustment. When the comp’s living area differs by more than 50 sqft, we apply the comp’s own improvement-only $/sqft (verifiable directly from public records for that comp):
Sqft Adj = (subject.sqft − comp.sqft) × (comp.improvement_value / comp.sqft)
Feature adjustments. When the comp differs from your property on pool, garage capacity, carport, covered patio, workshop, or condition rating, we apply standard residential adjustment values (consistent with what county appraisers use internally).
The Three-Strata Equity Reading
From a broader pool of eligible comparable properties — same neighborhood, ±25% sqft, ±15 years, within 2 miles — we surface three medians, sorted by appraised $/sqft:
- High strata (top 5 by $/sqft) — the conservative end of the defensible range.
- Middle strata (middle 5 by $/sqft) — the neutral middle of the same pool.
- Low strata (bottom 5 by $/sqft) — the most aggressive end of the defensible range.
All three medians come from the same neighborhood comp set. The spread between them shows how comp selection methodology drives the answer. The owner picks which stratum to present at the hearing based on their judgment.
Why Our Estimate Is a Range, Not a Point
We never tell an owner “you’ll save $X.” Two reasons:
Honest expectation-setting. Audited population data shows residential ARB outcomes cluster around a 5–7% median reduction, with about 1 in 8 informal protests resulting in no reduction at all. A precise dollar figure misrepresents that reality.
Tex. Bus. & Com. Code §17.46(b) (DTPA) compliance. Texas consumer-protection law restricts implied or guaranteed outcomes. Showing “estimated savings range” with disclosures is the safe-harbor presentation; quoting a precise number is not.
Sources: Squaredeal Tax Harris County 2017–2025 dataset; Ownwell three-year seven-county study; Kinder Institute / January Advisors cross-corroboration; HCAD 2024 Annual Report.
Audited Population Numbers
What the public data actually shows for residential ARB outcomes:
- ~5–7% median reduction for protests that result in any change.
- ~1 in 8 informal protests result in no reduction.
- In 2025 Harris County, DIY median dollar reduction was $20,640 versus $13,202 for agent-led filings (Squaredeal HCAD A1 dataset).
- DIY success rate in 2025 Harris was 71% (29% got no reduction).
- Approximately 35% of Harris County’s 1.12 million single-family homes filed a protest in 2025.
Results are not guaranteed. Many protests result in no reduction. Harris County data may not generalize 1:1 to other counties — use as directional support.
Verify Each Step Yourself
Every formula above uses public-record inputs. The neighborhood code, the comp’s improvement value, the per-acre rate, the lot acreage — all of these are searchable on your county’s public ArcGIS portal. You can reproduce our math comp-by-comp from the data we cite. That’s the point: the panel can verify it too.
See It Applied to a Real Property
Want to see what this looks like end-to-end? Download a complete sample evidence packet generated from this methodology — cover dashboard, three-strata equity table, sales table, adjustment rows, sourced comp data.
Download sample evidence packet (PDF) →See It Applied to Your Property
$50 for a complete evidence packet — same methodology, your data.
Montgomery, Harris, Dallas & Travis counties. $50 flat fee if you purchase a protest packet.