1. A company may file a claim for credit or refund of an overpayment of any tax imposed by this chapter within six months after the due date of the return or within six months after the return was filed, whichever period expires later.
2. A claim for credit or refund must be made by filing with the commissioner an amended return, or other report as prescribed by the commissioner, accompanied by a statement outlining the specific grounds upon which the claim for credit or refund is based.
3. The commissioner shall notify the company if the state board of equalization disallows all or part of a claim for credit or refund. The decision of the state board of equalization denying a claim for credit or refund is final and irrevocable unless the company brings an action against the state in district court within six months of the mailing of the notice denying the claim for credit or refund.