Mo. Rev. Stat. § 376.640
At any time after the payment of three or more full annual premiums, and not later than sixty days from the beginning of the extended insurance provided in section 376.630, the legal holder of any policy affected by section 376.630 may demand of the company, and the company shall issue, its paid-up policy, which, in case of an ordinary life policy, shall be for such an amount as three-fourths of the net value of the regular policy at the age and date of lapse, computed according to actuaries' or combined experience table of mortality, with interest at the rate of four percent per annum, without deduction of indebtedness on account of said policy, will purchase, applied as a net single premium upon the said table of mortality and interest rate aforesaid; and in case of a limited payment life policy, or of a continued payment endowment policy, payable at a certain time, or at death, it shall be for an amount bearing such proportion to the amount of the original policy as the number of complete annual premiums actually paid shall bear to the number of such annual premiums stipulated to be paid; provided, that from such amount the company shall have a right to deduct the net reversionary value of all indebtedness to the company on account of such policy; and provided further, that the policyholder shall, at the time of making demand for such paid-up policy, surrender the original policy, legally discharged, at the parent office of the company.
§ 376.640, RSMo