Mo. Rev. Stat. § 144.613
Notwithstanding the provisions of section 144.655, at the time the owner of any new or used boat or boat motor which was acquired after December 31, 1979, in a transaction subject to tax under this chapter makes application to the director of revenue for the registration of the boat or boat motor, he shall present to the director of revenue evidence satisfactory to the director of revenue showing the purchase price, exclusive of any charge incident to the extension of credit, paid by or charged to the applicant in the acquisition of the boat or boat motor, or that no sales or use tax was incurred in its acquisition, and, if tax was incurred in its acquisition, that the same has been paid, or the applicant shall pay or cause to be paid to the director of revenue the tax provided by this chapter in addition to the registration fees now or hereafter required according to law, and the director of revenue shall not issue a registration for any new or used boat or boat motor subject to tax in this chapter until the tax levied for the use of the same under this chapter has been paid.
§ 144.613, RSMo