72 Pa. Stat. § 6105.2
In order for any person who was or is entitled by law to redeem such property to receive the benefits of the installment system of payment authorized and provided by this act, they shall enter into a written agreement with the taxing authorities of the said political subdivision, which shall be prepared by the solicitor for such political subdivision, in the nature of a lease, which shall require at the time of signing the agreement the payment of all costs incident to the aforesaid tax sale and twenty per centum of the amount of all taxes and municipal claims and penalties and interest accrued thereon charged against said property, and the payment of the remainder of said amount of tax and municipal claims, penalties and interest in four equal installments, each of which shall be made within one year after the last day fixed by said agreement for the payment of the previous installment. Said agreement shall further require that the respective current taxes assessed on said real property for each year during such installment period shall be paid before a penalty attaches thereto.
72 P.S. § 6105.2