Haw. Rev. Stat. § 237-21
If any person, other than persons liable to the tax on manufacturers as provided by section 237-13(1), is engaged in business both within and without the State or in selling goods for delivery outside the State, and if under the Constitution or laws of the United States or section 237-29.5 the entire gross income of such person cannot be included in the measure of this tax, there shall be apportioned to the State and included in the measure of the tax that portion of the gross income which is derived from activities within the State, to the extent that the apportionment is required by the Constitution or laws of the United States or section 237-29.5. In the case of a tax upon the production of property in the State the apportionment shall be determined as in the case of the tax on manufacturers. In other cases, if and to the extent that the apportionment cannot be accurately made by separate accounting methods, there shall be apportioned to the State and included in the measure of this tax that proportion of the total gross income, so requiring apportionment, which the cost of doing business within the State, applicable to the gross income, bears to the cost of doing business both within and without the State, applicable to the gross income.
HRS § 237-21
Attorney General Opinions
Branch office of mainland travel agency subject to tax on certain portion of earnings. Att. Gen. Op. 65-6.
Tax on trucking business' gross receipts for services rendered wholly within the State not subject to apportionment.48 Haw. 486,405 P.2d 382. Apportionment found unnecessary where taxable income consisted of interest income derived from sale of land located in Hawaii.57 Haw. 436,559 P.2d 264. Federal Aviation Act preempts the State's ability to assess general excise taxes on revenues derived from the sale of "air transportation"; however, the State may assess general excise taxes under § 237-13(6) and this section on that portion of the gross receipts that a freight forwarder receives for ground transportation and other non-air services it provides.89 Haw. 51,968 P.2d 653.