If not later than 3 years after the date of payment of any amount as contributions or interest thereon, an employing unit which has paid such amount shall make application for an adjustment or refund thereof the commission shall determine whether such contributions or interest or any portion thereof was erroneously collected; and the employing unit shall be promptly notified of such determination, which shall become final unless the employing unit files with the commission an application for redetermination thereof in accordance with the provisions of section 32a. If it is finally determined, redetermined or otherwise decided that any amount thus at issue was erroneously collected, the commission shall allow such employing unit to make an adjustment thereof, without interest, in connection with subsequent contribution payments by him. If the adjustment cannot be made within the ensuing 3 months the commission shall refund the amount, without interest, from the appropriate fund or funds. For like cause, in the same manner, and within the same period, adjustment or refund may be made by the commission on its own initiative. When the individual owner of an employing unit who is entitled to a refund dies or is legally declared insane or mentally incompetent, the refund shall become due and payable to the person who appears to the commission upon investigation to be the legal heir or guardian of the individual owner, or to any other person found by the commission to be equitably entitled to the refund by reason of having incurred expenses in behalf of the individual owner for his burial or other necessary expenses.