Mo. Rev. Stat. § 408.036
Notwithstanding any other provision of this chapter to the contrary, no prepayment penalty shall be charged or exacted by a lender on any promissory note or other evidence of debt secured by residential real estate when the full principal balance thereof is paid after five years from the origination date and prior to maturity; and in no event shall any prepayment penalty exceed two percent of the balance at the time of prepayment, except for, when an existing mortgage loan is replaced with a new mortgage loan made by another lender and the proceeds from the new loan are used to either pay down or reduce the balance to a smaller amount before paying in full and in order to avoid or reduce the prepayment penalty. In such an occurrence the prepayment penalty shall not be more than two percent of the average daily balance for the prior six months, provided that the 1990 and 1992 reenactment of this section shall not be construed to be action taken in accordance with Public Law 96.221, Section 501(b)(4). Any fees received in excess of those permitted pursuant to this section shall be returned to the person from whom received upon demand. Business and corporate loans are not subject to the provisions of this section.
§ 408.036, RSMo