A friend recently received a “Notice of Increase in Assessment” on a property — not because of any renovation or improvement, but simply because they’d just purchased it for more than the last sale price. That raised an interesting question: in Pennsylvania, assessments don’t automatically change at the time of sale the way they do in many other states, and singling out a specific sale for reassessment is against the law. So what was going on?
It’s standard for a county to increase your assessment (and your taxes) when you improve a property — renovate a building, and expect an increase. But a jump triggered purely by a recent purchase price is a different situation, and it’s worth understanding how Pennsylvania’s system actually works.
1. Understand How Property Taxes Are Established
Pennsylvania has a constitutional requirement for uniformity of taxation. Counties are the governmental unit responsible for assessments, and they typically meet that uniformity requirement by adopting a “base year” market value — a countywide reassessment sets values as of a specific date, which becomes the base year, and the county applies a percentage to that value to calculate assessments.
Counties vary widely in how often they reassess. Lancaster County, for example, is required by statute to reassess every 8 years, while Lebanon County went 40 years between updates. Base years for several Central PA counties:
| County | Base Year |
|---|---|
| Lancaster County | 2015 (reassessed every 8 years by statute; last done in 2018) |
| York County | 2004 (100% of market value) |
| Adams County | 2010 (100% of market value) |
| Dauphin County | 2001 (100% ratio of assessment) |
| Cumberland County | 2010 (100% ratio of assessment) |
| Berks County | 1994 |
| Lebanon County | 2012 |
How Do You Know If Your Assessment Is Accurate?
Every Pennsylvania county has its assessments analyzed annually by the State Tax Equalization Board (STEB), which studies selling prices against assessed values to develop the “Common Level Ratio of Assessment” — a percentage showing the relationship between a county’s assessments and today’s market value. A new ratio is released around June 15 each year.
For example, if York County’s Common Level Ratio is 56.8% and your property’s actual market value today is $2,000,000, you’d calculate: $2,000,000 × 0.568 = $1,136,000 assessed value based on the 2004 base year. If your actual assessment is lower than that number, you may be under-assessed.
2. Know How Governing Bodies Base an Appeal
Most appeals to increase a property’s taxes are filed by school districts, since school taxes are typically the largest share of the bill and districts have the most incentive to pursue reassessment.
An assessment can technically be revised at any time for “cause” — typically a physical change to the property, like a new addition or major renovation, that enhances market value. Normal maintenance, like painting or a new roof, does not trigger reassessment, and any revised value must still represent the base year market value to preserve uniformity.
Increasingly, though, school districts are challenging assessments based purely on recent sales — for example, noticing a property sold for $500,000 but is assessed at only $250,000, then filing an appeal arguing the assessment is out of line with the sale price. What districts are really doing here isn’t seeking true current market value — it’s trying to push the assessed value up to match the base year value implied by that sale.
There’s a real legal question about whether these “recent sales” appeals hold up under Pennsylvania’s uniformity requirement. Taxing entities have generally gotten around that argument by applying a consistent standard — for instance, only appealing properties that recently sold and are assessed below 80% of the purchase price. That sounds reasonable in principle, but it can produce uneven outcomes: two similar properties assessed at $300K each, one sells for $600K and gets appealed (and pays roughly double in property tax), while the other — never sold — stays untouched.
3. Understand the Burden of Proof
Whoever files an appeal carries the burden of proof — when a school district appeals a property owner’s assessment, the burden is on the district. Specifically, the filing party must prove the subject property’s market value is inaccurate (too high or too low), using a recognized valuation method. Pennsylvania recognizes three:
- Comparable sales approach — using sale prices (not assessments) of similar properties as evidence.
- Cost approach — based on construction costs, typically applicable mainly to new construction.
- Income approach — analyzing a property’s net operating income and applying a capitalization rate to determine fair market value.
Importantly, a sale price alone does not meet the burden of proof for a tax appeal filed by a taxing entity. A recent purchase price is persuasive, but not conclusive — a school district can’t change an assessment simply by submitting a copy of the deed. The evidence must include comparable sales or another recognized valuation method.
The core question in most appeals is fair market value — either as of the current year (with the Common Level Ratio applied) or as of the county’s base year — and whoever files the appeal can choose which argument to make at the hearing. The base year argument looks at the property’s value as of the base year directly; the fair market value (FMV) approach determines current market value, then applies the (annually changing) Common Level Ratio backward to arrive at an equivalent base year assessment. Taxing entities tend to favor the FMV approach, since it lets them point to a recent sale price as evidence — but property owners can counter with evidence of the property’s actual base year value.
Example: A property in Lancaster County is assessed at $547,200, with a Common Level Ratio of 1.66. $547,200 × 1.66 = $908,352 in implied market value. If the property is worth less than that, it may be over-assessed; if worth more, it may be under-assessed.
If you’ve received a notice of increased assessment, compare your property’s base year value to its current fair market value (adjusted by the Common Level Ratio) to see whether the base year data supports a case for a lower assessment.
The Bottom Line
Property taxes are usually the largest ongoing cost on a real estate investment, so understanding how assessments and appeals actually work is worth the time. Knowledge of the base year, the Common Level Ratio, and the burden of proof can make the difference between overpaying and successfully defending — or winning — an appeal.
