72 Pa. Stat. § 5971w
Whenever any county, city, borough, town, township, school, or poor taxes, on seated lands, for the tax year one thousand nine hundred and thirty-four or any previous year, have been returned to the county commissioners, and such taxes have not been paid in full, and no sale for such taxes has been held, all such taxes so returned shall be liens on the real estate upon which they were liens at the time of such returns, for a period of five years from the effective date of this act: Provided, That any such lien be filed in the office of the prothonotary of the proper county within one year after the effective date of this act; and thereafter the revival, preservation, and enforcement of said lien shall be governed in all respect by the provisions of the act of May sixteenth, one thousand nine hundred twenty-three (Pamphlet Laws, two hundred seven).
72 P.S. § 5971w