(1) The effect of RCW 30A.26.010 through 30A.26.050, 30A.26.070 through 30A.26.100, and 30A.26.130 may not be varied by agreement, except as provided in those sections. Subject to subsection (2) of this section, the effect of RCW 30A.26.060, 30A.26.110, and 30A.26.120 may be varied by agreement.

(2) A provision in an account agreement or other record that substantially excuses liability or substantially limits remedies for failure to perform an obligation under this chapter is not sufficient to vary the effect of a provision of this chapter.

(3) If a beneficiary is a party to an account agreement, the bank and the depositor may amend the agreement without the consent of the beneficiary only if the agreement expressly permits the amendment.

(4) If a beneficiary is not a party to an account agreement and the bank and the depositor know the beneficiary has knowledge of the agreement's terms, the bank and the depositor may amend the agreement without the consent of the beneficiary only if the amendment does not adversely and materially affect a payment right of the beneficiary.

(5) If a beneficiary is not a party to an account agreement and the bank and the depositor do not know whether the beneficiary has knowledge of the agreement's terms, the bank and the depositor may amend the agreement without the consent of the beneficiary only if the amendment is made in good faith.