Hawaii Revised Statutes Division 1. Government § 236D-13

Whenever the tax due under this chapter is proved to have been overpaid, the department shall refund the amount of the overpayment, together with interest at the then existing statutory rate of interest in the manner provided in section 231-23(c). No claim for refund may be initiated more than two years after the date the federal tax has been finally determined.

As to all tax payments for which a refund or credit is not authorized by this section (including, without prejudice to the generality of the foregoing, cases of unconstitutionality), the remedies provided by appeal or by section 40-35 are exclusive.