72 Pa. Stat. § 5781
After June first, 1888, all taxes levied upon unseated lands, within the counties of this commonwealth, shall be paid by the owner or owners of such unseated lands within the year for which the same are levied; and in case of the refusal or failure of any person or persons, companies or bodies corporate, owner or owners of such unseated lands to pay the taxes so levied within the year for which the same are levied and collectible, then interest at the rate of six per centum per annum is to be charged upon the amount of said taxes, or any part thereof, remaining due and unpaid from and after the first day of the year following that for which said taxes were levied until the same has been paid in full, or the land sold as now provided by law for the sale of unseated lands: Provided, No interest shall be charged upon taxes levied for the years 1886 and 1887.
72 P.S. § 5781