53 Pa. Stat. § 30902
Where the respective treasurer has not already in his hands, the duplicates of said taxes or certificates or schedules thereof, it shall be the duty of any receiver or collector of taxes, or other person having such delinquent taxes in his hands, to certify to the said city treasurer schedules of all unpaid taxes, with description of the property assessed, and it shall be the duty of the city treasurer to advertise for sale all the lands upon which it appears the taxes have not been paid as shown by the duplicates in his hands, or by the returns, or schedules certified to him as aforesaid. Said advertisement shall be made once a week for three successive weeks prior to the day of sale in at least two newspapers of general circulation, and in the legal newspaper printed and published in the respective city. The treasurer shall also cause to be posted or tacked in a conspicuous place on each parcel or lot of land, advertised for sale, at least ten days prior to the day of sale, a notice stating that said lands will be sold by said treasurer for delinquent taxes on a certain day and time and at a certain place within the city, for which posting of notice he shall receive and tax as costs one dollar ($1). No sale shall be valid where the taxes have been paid prior to said advertisement or where the taxes and costs have been paid after advertisement and before sale.
53 P.S. § 30902