Wash. Rev. Code § 11.104B.220
(1) This section applies to a business or other activity conducted by a fiduciary if the fiduciary determines that it is in the interests of the beneficiaries to account separately for the business or other activity instead of:
(3) A fiduciary that accounts separately under this section for a business or other activity:
(a) May determine:
(i) The extent to which the net cash receipts of the business or other activity must be retained for:
(4) Activities for which a fiduciary may account separately under this section include:
[ 2021 c 140 s 2403.]