What is an accurate property assessment?

Ideally, homes are assessed at 100% of their market values. That’s what happens immediately after a countywide reassessment.

But assessment values become inaccurate over time as the real estate market changes. To keep new assessments in line with old ones, the PA Department of Revenue sets a Common Level Ratio factor for each county every July.  

For example, Montgomery County has a 2021-2022 common level ratio factor of 2.24, meaning market value should equal 2.24 times the assessment.  Doing the math in reverse, Montco assessments should equal about 44.643% of market value.  So, a home with a market value of $100,000 would be assessed at about $44,643, and that assessed value would be used to calculate local property tax bills.

Here’s the math behind that percentage:

If you want to figure out the market value that the county is using — meaning, you want to know what the county thinks a property is worth — multiply the assessed value by the common level ratio factor.  Using the Montgomery County example above: $44,643 (assessed value) x 2.24 (ratio) = $100,000 (market value as determined by county).

This Philadelphia Inquirer article provides more explanation on assessments and appeals in the Greater Philadelphia region.

 * Delaware County just completed a court-ordered countywide reassessment, the values of took effect in 2021. Learn more about that in our blog post:  Delco reassessment project: an overview.