Once an individual trust account is funded, the primary donor cannot amend the joinder agreement to change the disposition plan. A change to the disposition plan may be made only by court order or other dispute resolution mechanism available under state law, including a nonjudicial resolution of dispute agreement under chapter 11.96A RCW. The nonjudicial resolution could be an agreement signed by all of the interested parties changing the terms of the disposition plan of a developmental disabilities endowment trust fund individual trust account. The agreement needs to be in writing, state that it is being made pursuant to RCW 11.96A.220, set forth the change that is being made to the trust, and be signed by the primary donor (if alive), the trustee, and all beneficiaries (current and residual) of the trust account.