72 Pa. Stat. § 5970
All tax sales heretofore held by any county treasurer of the eighth class within this Commonwealth of seated lands for unpaid taxes under section forty-one of an act entitled "An act to reduce the State debt, and to incorporate the Pennsylvania canal and railroad company," approved the twenty-ninth day of April, one thousand eight hundred and forty-four (Pamphlet Laws, four hundred eighty-six), and under the acts amendatory thereof, be and the same are hereby ratified, confirmed, and made valid, notwithstanding the fact that no demand by the collector for the payment of the tax was made on the owner individually: Provided, Four years have elapsed since the date of said sale and the other necessary steps leading up to said sale were regular.
All deeds acknowledged and delivered by the county treasurer by virtue of said seated tax sales are hereby made valid four years after the date of said tax sales: Provided, There has been no redemption of the land sold: And provided further, That all the other requirements of the law concerning such tax sales and the acknowledgment and delivery of deeds for the land sold at said sales have been complied with.
72 P.S. § 5970