Upon application by an operator, if the Commissioner determines that any tax, interest, or penalty has been paid more than once, or has been erroneously or illegally collected or computed, the same shall be credited by the Commissioner on any taxes then due from the operator under this chapter, and the balance shall be refunded to the operator or his or her successors, administrators, executors, or assigns, together with interest at the rate per annum established from time to time by the Commissioner pursuant to section 3108 of this title. That interest shall be computed from the latest of 45 days after the date the return was filed, 45 days after the date the return was due, including any extensions of time thereto, with respect to which the excess payment was made, or, if the taxpayer filed an amended return or otherwise requested a refund, 45 days after the date such amended return or request was filed. Provided, however, no such credit or refund shall be allowed after three years from the date the return was due. (Added 1959, No. 217, § 10; amended 1975, No. 154 (Adj. Sess.), § 5, eff. date, see note below; 1979, No. 105 (Adj. Sess.), § 32; 1983, No. 59, § 5, eff. April 22, 1983; 2015, No. 57, § 90, eff. June 11, 2015.)