Delaware County has been ordered to reassess all of its residential and commercial properties, effective Jan. 1, 2021, after a trial judge found the county violated the state constitution as a result of going nearly two decades without a reassessment.

Two Delaware County families whose new homes were assessed at what they said were exceedingly high percentages of their fair market values argued that the county has been improperly using 1998 as its base year for assessments, leading to “a system of property taxation that is profoundly inequitable in direct violation of the uniformity clause of the Pennsylvania Constitution,” according to court papers.