If not later than 4 years from the last day of the period with respect to which a payment of any contributions or interest thereon was made, or one year from the date on which such payment was made, whichever shall be the later, an employing unit or employer who has paid such contribution or interest thereon shall make application for an adjustment thereof in connection with subsequent contribution payments, or for a refund thereof because such adjustment cannot be made, and the commissioner shall determine that such contributions or interest or any portion thereof was erroneously collected, the commissioner shall allow such employing unit or employer to make an adjustment thereof, without interest, in connection with subsequent contribution payments by him; or, if such adjustment cannot be made, the commissioner shall refund said amount, without interest, from the fund, unless such payments are to be refunded from the contingent fund as provided in N.H. Rev. Stat. § 282-A:140. The commissioner, on his own initiative, may, in any case, for like cause and within the same period, allow either adjustment or refund, as he in his discretion may deem to be for the best interests of the state. Nothing in this chapter or in any part thereof shall be construed to authorize any refund or credit of monies due and payable under the law and rules in effect at the time such monies were paid. It being further provided that the amount to be refunded or adjusted shall be reduced by the amount of unemployment compensation benefits which would not have been paid except for the erroneously reported employment and wages.