72 Pa. Stat. § 9169
Unless suit for collection of the taxes imposed by this article is instituted within twenty years after any tax becomes delinquent, the lien shall cease as to any purchaser, mortgagee or lessee of a devisee or heir of, or a beneficiary under a deed of trust of, the real property subject to the lien. Any time within the twenty-year period, if any tax on the real property is not paid, the department shall have power to file a certificate, under its seal, certifying to nonpayment which, when filed in the office of the clerk of the county where the real property is situated, shall continue the lien against decedent's real property for an additional period of five years from the date of the filing and the lien shall be indexed in the office of the clerk. If the taxes on the real property are not paid within the additional period of five years, the department shall have power to extend the lien for additional periods of five years by filing a certificate in the manner provided in this section.
72 P.S. § 9169