53 Pa. C.S. § 8818
(a) Assessment of lands divided by county boundary lines.--
(1) If county boundary lines divide a tract of land, the land will be assessed in the county in which the mansion house is located.
(2) If county boundary lines pass through the mansion house, the owner of the land may choose the county in which the property will be assessed. If the owner refuses or fails to choose the county in which the property will be assessed, the county in which the larger portion of the mansion house is located has the right of assessment.
(3) If vacant land is divided by the boundary lines of two counties, the land shall be assessed in each county in which it is located.
(b) Assessment of lands divided by township boundary lines.--
(1) If land is divided by the boundary lines of a township and a city, a township and a borough or a township and a town, and the mansion house is located in the township, all of the land will be assessed in the township.
(2) If land is divided by the boundary lines of a township and a city, a township and a borough, a township and a town or two townships, and the mansion house is located in the city, borough, town or one township, then the land shall be assessed in the municipality in which it actually lies.
(3) If vacant land is divided by the boundary lines of two townships, the land shall be assessed in each township in which it is located.
(c) Assessment where township boundary lines pass through mansion house.--If the boundary lines of any township and a city, borough or township pass through the mansion house, the owner of the land may choose the municipality in which the land shall be assessed. If the owner refuses or neglects to choose, the mansion house shall be considered to be entirely located in the township for assessment purposes.
(d) Assessment where lands are divided by boundary lines between cities, boroughs or cities and boroughs.--
(1) If lands are divided by the boundary lines of two or more cities, two or more boroughs, or one or more cities and one or more boroughs, the lands shall be assessed in the city or borough in which the mansion house is located.
(2) If the boundary lines pass through the mansion house, the lands shall be assessed in the city or borough in which the larger portion of the mansion house is located.
(3) If vacant land is divided by the boundary lines of two or more cities, two or more boroughs, or one or more cities and one or more boroughs, the land shall be assessed in each municipality in which it is located.
(e) Assessment of coal underlying lands divided by county, city, township or borough boundary lines.--Where coal is lying underneath lands that are divided by county, city, township or borough lines, and the ownership of the coal has been severed from the ownership of the strata or surface, the county assessment office shall assess each division of coal in the municipality in which it actually lies.
53 Pa.C.S. § 8818