Mo. Rev. Stat. § 461.021: Beneficiary designation under written instrument or law, effect.

A beneficiary designation, under a written instrument or law, that authorizes a transfer of property pursuant to a written designation of beneficiary, transfers the right to receive the property to the designated beneficiary who survives, effective on death of the owner, if the beneficiary designation is executed and delivered in proper form to the transferring entity prior to the death of the owner.