Mo. Rev. Stat. § 140.610
In all suits and controversies involving the title of land claimed and held by virtue of the deed executed by the county collector for nonpayment of taxes thereon, under this tax law, the person claiming by adverse title to such deed shall be required to prove, in order to defeat the title conveyed by such deed, either that the land described therein was not subject to taxation at the date of assessment of the tax for which it was sold, or that the taxes for the nonpayment of which the land was sold were paid to the proper officer within the time limited by law therefor, or that the same had not been assessed for the taxes for the nonpayment of which it was sold, or that the same had been redeemed pursuant to law, or that a certificate in proper form had been given by the proper officer, within the time limited by law for paying taxes or for redeeming from sales made for the nonpayment thereof, stating no taxes were due at the time such sale was made, or that at the date of the deed the redemption period had not expired.
§ 140.610, RSMo