61 Pa. Code § 6.13 – Overpayment, refund and interest.

(a) Interest will not be allowed on an overpayment of an eligible tax liability or an eligible interest liability if the overpayment is refunded or credited to a taxpayer’s account within 180 days after the tax amnesty return is filed.
(b) A refund of an overpayment of an eligible tax liability or an eligible interest liability will not be granted unless the overpayment is the result of a mathematical or clerical error.
(c) A refund or credit will not be allowed for eligible penalty liability paid to the Department prior to the amnesty period.