Every number in the dashboard traces back to one of five steps. Public records in, ranked appeal candidates out — with the math validated against actual published tax bills to a median error of 0.11%.
Most states reassess every few years. Pennsylvania doesn’t. Montgomery County’s last full reassessment was 1996. Assessed values are still pegged to what properties were worth almost three decades ago.
To bridge the gap between 1996 values and today’s market, the state publishes a number called the Common Level Ratio (CLR). It tells you what fraction of current market value the assessed value represents.
Plain English: a property assessed at $1M means the county is implicitly saying it thinks the property is worth roughly $3.25M in 2026 dollars. If the actual market value is below that, the property is over-assessed.
The CLR is published by the Pennsylvania State Tax Equalization Board every July. We re-verify against the official PDF on each refresh.
No one step does it alone. The screen works because each layer compounds — CLR translates 1996 to 2026, the income approach gives an independent value, and exact mills convert the gap into real annual dollars.
Back-derive what today’s market value would have to be for the assessment to be fair under the current CLR.
Compute the property’s actual market value from rent, vacancy, expenses, and cap rate.
Compare the two values. If income approach is materially lower, the property is a screening candidate.
Multiply real market value by CLR to get the assessment the property should have today.
Reduction × exact mill rate × 0.65 damping factor for realistic settlement.
From the assessed value alone, we derive what the county implicitly thinks the property is worth today:
implied_market_value = assessed_value ÷ CLRThis is a back-derived number. It tells us: what would the property need to be worth in 2026 dollars for the 1996 assessment to be fair under today’s CLR?
This is one side of the equation. To find an over-assessment, we need a second, independent estimate of true market value.
For commercial properties, market value is best estimated by the income approach — the same method professional appraisers use, and the method PA appeal boards weight most heavily for commercial appeals.
gross_potential_income = sqft × market_rent_psfEach input is sourced from CBRE, Cushman & Wakefield, and Colliers Q4 2025 / Q1 2026 suburban Philadelphia market reports:
| Property class | Market rent / SF | Vacancy | Opex | Cap rate |
|---|---|---|---|---|
| Office | $24 | 15% | 40% | 9.0% |
| Retail | $22 | 10% | 25% | 7.5% |
| Industrial | $11 | 5% | 20% | 7.0% |
| Warehouse | $11 | 5% | 20% | 7.0% |
| Mixed-Use | $20 | 10% | 30% | 8.0% |
| Multifamily | $22 | 7% | 42% | 6.0% |
Where our data provider’s published AVM differs materially from its placeholder pattern (~1.02× assessed for 76% of MontCo records), we use the AVM instead. Otherwise the income approach is the anchor.
A property qualifies as a screening candidate when:
If the income approach is right, what should the property’s assessment be under today’s CLR?
fair_assessment = income_approach_market_value × CLRThe difference between the current assessment and the fair assessment is what an appeal would aim to recover.
Annual savings comes from multiplying the assessment reduction by the property’s exact mill rate. In Pennsylvania, total mills = county + municipality + school district:
assessment_reduction = current − fair_assessmentThe 0.65 damping factor reflects the reality of PA Board of Assessment Appeals decisions. Boards rarely grant the full claimed reduction — typical settlements land at 60–75% of the claim. We use 0.65 (mid-range) as the realistic expectation.
Each property uses its exact total mill rate, not a county-wide average. The lookup is keyed first by city + ZIP (validated against actual published tax bills), with a school-district average as fallback.
| Assessed value (1996 base) | $25,991,000 |
| $25,991,000 ÷ 0.3076 | $84,496,099 |
| Income-approach market value | $53,672,264 |
| Implied market | $84,496,099 |
| Income approach | $53,672,264 |
| Gap dollars | $30,823,835 |
| Gap % | 57.4% |
| $53,672,264 × 0.3076 | $16,509,588 |
| Reduction: $25,991,000 − $16,509,588 | $9,481,412 |
| Total mills (Lower Merion Twp) | 46.0384 |
| Undamped: × 46.0384 ÷ 1000 | $436,510 |
| Expected savings (× 0.65 damping) | $283,731 / yr |
Mill rates and CLR aren’t trusted blindly. We verify against the truth — actual published tax bills — every time the data is refreshed.
When a city or municipality is missing from the lookup table, we back-derive the rate from the actual bill data — hundreds of properties’ tax/assessed ratios converge on a single muni mill value, which we then add to the table. CLR is re-verified against the latest STEB publication every July.
Comps are ranked: building-sqft matches first, lot-only fallbacks last; same-ZIP first, then adjacent; smallest sqft difference; most recent sale. We deliver up to 6 per lead, prioritizing the strongest evidence.
We classify each subject property’s last sale by deed type:
| Class | Deed types | Use as evidence? |
|---|---|---|
| arm_s_length | Warranty, Grant, Bargain & Sale (price ≥ $10K) | Board-quality |
| estate_or_intra | Quitclaim, Executor, Trustee, Personal Rep | Not market-validated |
| distressed | Sheriff, Tax, Foreclosure, Deed in Lieu | Below-market by definition |
| unverified | Unclear deed type or price under $10K | Likely nominal transfer |
| no_sale | No transaction on record | Use comps only |
Properties with a recent arm’s-length sale below the CLR-implied market value are flagged as slam-dunks — the sale price itself is the appeal evidence, no comp argument needed.
This is a screening tool, not a final appraisal.
The numbers shown represent a credible candidate assessment for appeal — not a hearing-grade valuation. The income approach uses class-average market rent, vacancy, and cap rate, not the property’s actual rent rolls and operating statements. We expect a 20–30% false positive rate at this stage; that’s normal for pre-engagement screening.
Before filing a formal appeal, the attorney should re-underwrite the lead with actual rent rolls, operating expenses, and a verified mill rate for the exact parcel.
The point of this product is to surface, at scale, the candidates that warrant that re-underwriting effort — not to replace it. Manual prospecting finds maybe 5–10 viable candidates per attorney per month. This system surfaces 100–300 in the same window. The attorney’s job is to filter and pursue; ours is to make the filter set as accurate as commercially possible.
Replacement Guarantee. Reject up to 25% of any batch within 30 days. We swap rejected leads 1:1 for fresh candidates from the same county. List price holds. The cap matches the structural false positive rate above — we replace because we’re confident in the screen, not because we’re hedging.