Haw. Rev. Stat. § 557A-503: Transfers from income to principal for depreciation.

(a) As used in this section, "depreciation" means a reduction in value of a fixed asset having a useful life of more than one year, due to wear, tear, decay, corrosion, or gradual obsolescence.

(b) A trustee may transfer to principal a reasonable amount of the net cash receipts from a principal asset that is subject to depreciation, but a transfer may not be made for depreciation:

(1) Of that portion of real property used or available for use by a beneficiary as a residence or of tangible personal property held or made available for the personal use or enjoyment of a beneficiary;

(2) During the administration of a decedent's estate; or

(3) Under this section if the trustee is accounting under section 557A-403 for the business or activity in which the asset is used.

(c) An amount transferred to principal need not be held as a separate fund.