Haw. Rev. Stat. § 235-93.4: Effect of civil union.

All provisions of the Internal Revenue Code referred to in this chapter that apply to a husband and wife, spouses, or person in a legal marital relationship shall be deemed to apply in this chapter to partners in a civil union with the same force and effect as if they were "husband and wife", "spouses", or other terms that describe persons in a legal marital relationship.