53 Pa. C.S. § 8425
(a) General rule.--A taxpayer who has paid an eligible tax to a local taxing authority may file a written request with the local taxing authority for refund or credit of the eligible tax. A request for refund shall be made within three years of the due date for filing the report as extended or one year after actual payment of the eligible tax, whichever is later. If no report is required, the request shall be made within three years after the due date for payment of the eligible tax or within one year after actual payment of the eligible tax, whichever is later.
(1) For purposes of this section, a tax return filed by the taxpayer with the local taxing authority showing an overpayment of tax shall be deemed to be a written request for a cash refund unless otherwise indicated on the tax return.
(2) A request for refund under this section shall not be considered a petition under section 8430 (relating to administrative appeals) and shall not preclude a taxpayer from submitting a petition under section 8431 (relating to petitions).
(b) Notice of underpayment.--For amounts paid as a result of a notice asserting or informing a taxpayer of an underpayment, a written request for refund shall be filed with the local taxing authority within one year of the date of the payment.
53 Pa.C.S. § 8425