53 Pa. Stat. § 30909
After the period for redemption, as provided for in this act, has expired and the said lands have not been redeemed, it shall be the duty of the city treasurer to certify to the board or boards of assessors, or proper assessing authorities charged with the duty of assessing such real estate for purposes of taxation, that he sold the lands to the grantee named in the deed, and that the period for redemption has expired, and said lands have not been redeemed, and if the said lands have been sold to the city, the aforesaid assessing authorities shall not thereafter return said lands for purposes of taxation, and no taxes shall be levied thereon as long as the property is held and owned by the city. Copies of the aforesaid certification may also be furnished to deed registries or other interested authorities.
53 P.S. § 30909