Mo. Rev. Stat. § 142.866: Consumer liable, when — vendor liable, when.

1. In the event the tax imposed by section 142.803 is not otherwise precollected, the ultimate consumer shall be liable, unless such person is otherwise exempted pursuant to section 142.869 or subdivisions (3) and (5) of subsection 2 of section 142.815, for the tax upon the delivery into the fuel supply tank of a motor vehicle for the use of motor fuel on the highways including, but not limited to:

(1) Any diesel fuel that contains a dye; or

(2) Any motor fuel on which a claim for refund has been made.

2. The ultimate vendor of motor fuel, other than a federally recognized Indian tribe, shall be jointly and severally liable for the backup tax precollected by subsection 1 of this section if the ultimate vendor knows or has reason to know that the motor fuel, as to which tax imposed by this chapter has not been paid, is or will be consumed in a nonexempt use.