Mo. Rev. Stat. § 456.5-506: Mandatory distribution defined — overdue distribution.

1. As used in this section, "mandatory distribution" means a distribution of income or principal which the trustee is required to make to a beneficiary under the terms of the trust, including a distribution upon termination of the trust. The term does not include a distribution subject to the exercise of the trustee's discretion even if (1) the discretion is expressed in the form of a standard of distribution, or (2) the terms of the trust authorizing a distribution couple language of discretion with language of direction.

2. Whether or not a trust contains a spendthrift provision, a creditor or assignee of a beneficiary may reach a mandatory distribution of income or principal, including a distribution upon termination of the trust, if the trustee has not made the distribution to the beneficiary within a reasonable time after the required distribution date.