Mo. Rev. Stat. § 408.031: Fee in lieu of interest may be charged on loan — exception.

In lieu of the rate established under section 408.030, parties may agree in writing to a fee of ten dollars on any loan; provided, however, that no lender shall permit any borrower to be indebted to such lender on two or more contracts at any given time for the purpose or with the result of contracting for or receiving fees exceeding that permitted by this section.