53 Pa. Stat. § 17042
There shall be an allowance to all payers of taxes who shall pay the same in the year for which they are assessed, as follows: Five per cent. if paid on or before the first day of April; four per cent. if paid on or before the first day of June; two per cent. if paid on or before the first day of July. If paid after the first day of July and on or before the first day of September, no deduction shall be made; if paid after the first day of September and on or before the first day of October, an addition of two per cent. shall be added to and payable on the same, and if not paid until the first day of December, then an addition of five per cent. shall be added to and payable on the same; and the councils of Philadelphia shall have the power to allow any other percentage for the payment of taxes, or add any other penalty for their non-payment during the current year.
53 P.S. § 17042