72 Pa. Stat. § 1894
Whenever any corporation, limited partnership, joint-stock association, or company, incorporated or formed under the laws of this Commonwealth, and liable to the payment of tax upon its capital stock, or specifically exempted therefrom under the laws of this Commonwealth, shall own, either directly or through subsidiary or sub-subsidiary corporations, a majority of the total issued and outstanding shares of voting stock of any corporation, limited partnership, joint-stock association or company, then, in such cases, so much of the value of all shares of stock, so owned in such other corporation, limited partnership, joint-stock association, or company, as represents property or assets located or having a legal situs without this Commonwealth, shall not be liable to taxation, under the laws of this Commonwealth providing for the taxation of capital stock of corporations, limited partnerships, joint-stock associations, and companies, but shall be excluded in determining the value of the capital stock of such owning company for purposes of taxation.
72 P.S. § 1894