Haw. Rev. Stat. § 235-117
Notwithstanding section 235-116, the department may permit the Secretary of the Treasury of the United States, the Commissioner of Internal Revenue, the Multistate Tax Commission, or the proper officer of any state or territory imposing an income tax upon incomes of persons taxable under this chapter, or any county of this State, or the authorized representatives thereof to inspect the income tax returns and estimates of any such person for tax purposes only. The department may also furnish to these authorized persons an abstract of an income tax return or estimate or supply these persons with information concerning any item of income contained in a return or disclosed by the report of an investigation of the income or return of a taxpayer. The Multistate Tax Commission may make the information available to a duly accredited tax official of the United States, any state or territory, or the authorized representative thereof, for tax purposes only.
HRS § 235-117