Mo. Rev. Stat. § 408.405: Defenses or setoffs arising from transaction good against holder of security instrument, when.

The rights of a holder or assignee of an instrument, account, contract, right, chattel paper or other writing other than a check or draft, which evidences the obligation of a natural person as buyer, lessee, or borrower in connection with the purchase or lease of consumer goods or services, are subject to all defenses and setoffs of the debtor arising from or out of such sale or lease, notwithstanding any agreement to the contrary, only as to amounts then owing and as a matter of defense to or setoff against a claim by the holder or assignee; provided, however, with respect to goods only, the rights of the debtor under this section may be asserted to the seller at the address at which he did business at the time of the sale and must be so asserted within ninety days after receipt of the goods.