53 Pa. Stat. § 17046
In the month of January annually, the said receiver shall in books to be called "the register of unpaid taxes on real estate," register all unpaid taxes, (except occupation taxes,) of the preceding year; and the said taxes are hereby declared to be a lien on all real estate in accordance with the provisions of the act of February 3, 1824, entitled "An act relating to taxes on certain real estate in the city and county of Philadelphia;" * * * and the said receiver of taxes shall place in the hands of the city solicitor a list of all registered taxes unpaid in the month of January, every two years succeeding the year for which said taxes were levied and furnished to the said solicitor, bills for said taxes; and he shall enforce payment thereof by the sale of the real estate upon which the said taxes are a lien, and the said solicitor shall pay to the said receiver all moneys collected by him for taxes by the sale of such real estate monthly, and the said receiver shall enter satisfaction therefor on the register books; the city controller shall immediately after the expiration of the term of office of the receiver of taxes, audit his accounts, and make allowance for uncollected taxes, and all real estate sold by order of the orphans' court, if returned to and confirmed by the said court, shall be certified to the receiver of taxes by the prothonotary of said court, and all real estate sold by order of the court of common pleas or any other court, (except sold by the sheriff,) if returned to said court or courts and confirmed by said court or courts, shall be certified to the receiver of taxes by the prothonotary of said courts.
53 P.S. § 17046