53 Pa. Stat. § 7321
All interest charges, expenses and fees added to any and all delinquent county, city, borough, town, township, school district or poor district claims, imposed or assessed on any parcel or parcels of real estate in the year one thousand nine hundred and thirty-five and all previous years, arising out of or resulting from a service supplied, work done or improvement authorized and undertaken by any such political subdivision, or filed to recover for the grading, guttering, macadamizing, or otherwise improving the cartways of any public highway; for grading, curbing, recurbing, paving, repaving, constructing or repairing the footways thereof; for laying water pipes, gas pipes, culverts, sewers, branch sewers, or sewer connections therein; for assessments for benefits in the opening, widening or vacation thereof, or in the changing of watercourses, or the construction of sewers through private lands, or in highways of townships of the first class, or in the acquisition of sewers and drains constructed and owned by individuals or corporations, and of rights in and to use the same; for the removal of nuisances; or for water rates, lighting rates or sewer rates, may be abated by the political subdivision, in behalf of which the claim was filed, if said delinquent claims are paid as hereinafter provided.
In order to receive the benefits of this act, twenty per centum of the delinquent municipal claims, imposed or assessed on any parcel or parcels of real estate in the year one thousand nine hundred and thirty-five and in all previous years, shall be paid, on or before the thirty-first of December, one thousand nine hundred and thirty-seven; twenty per centum, on or before the thirty-first day of December, one thousand nine hundred and thirty-eight; twenty per centum, on or before the thirty-first day of December, one thousand nine hundred and thirty-nine; twenty per centum, on or before the thirty-first day of December, one thousand nine hundred and forty; and twenty per centum, on or before the thirty-first day of December, one thousand nine hundred and forty-one.
If and whenever any of the said installments are not paid when due and payable as herein provided, then, and in that event, there shall become due and payable for such year a sum equal to one-fifth of the total amount of the abated interest charges, expenses and fees in addition to the other payments required to be paid under this act during that year, which said additional sum shall be payable and must be paid at the time next succeeding installment payment becomes due under this act. If such additional sum is not so paid, then the total amount of the abated interest charges, expenses and fees, less the aggregate of any such additional sums theretofore paid, shall be revived and added to the unpaid claims with the same force and effect as if such abated interest charges, expenses and fees, or portion thereof, had never been abated, and the person liable for the payment thereof shall not thereafter be entitled to any further benefits or privileges under this act.
53 P.S. § 7321