Every building and loan association, not incorporated under the laws of this Commonwealth but doing business within this Commonwealth, shall, in the reports required to be made by it, make report of the amount of its stock outstanding, at the time of such reports, and held by residents of Pennsylvania, entitled to receive cash dividends or interest. Every such building and loan association, at the time of making every return required by this section, shall compute and pay the tax due to the Commonwealth upon its full-paid, prepaid and fully matured and partly matured stock, as required by law.
72 P.S. § 718