(a) Whenever the amount due upon assessment or review is less than the amount paid to the department on account thereof, the department shall enter a credit in the amount of such difference to the account of the person who paid the tax.(b) Where there has been no assessment of unpaid tax, the department shall have the power, and its duty shall be, to hear and decide any application for refund and, upon the allowance of such application, to enter a credit in the amount of the overpayment to the account of the person who paid the tax. Such application must be filed under Article XXVII .1971, March 4, P.L. 6, No. 2, § 1113-C, added 1986, July 2, P.L. 318, No. 77, § 17, imd. effective. Amended 1997, May 7, P.L. 85, No. 7, § 19, effective 7/1/1997; 2006, Oct. 18, P.L. 1149, No. 119, § 25, imd. effective.