Mo. Rev. Stat. § 143.151
For all taxable years beginning before January 1, 1999, a resident shall be allowed a deduction of one thousand two hundred dollars for himself or herself and one thousand two hundred dollars for his or her spouse if he or she is entitled to a deduction for such personal exemptions for federal income tax purposes. For all taxable years beginning on or after January 1, 1999, a resident shall be allowed a deduction of two thousand one hundred dollars for himself or herself and two thousand one hundred dollars for his or her spouse if he or she is entitled to a deduction for such personal exemptions for federal income tax purposes, provided that the exemption amount as defined under 26 U.S.C. Section 151 is not zero. For all tax years beginning on or after January 1, 2017, a resident with a Missouri adjusted gross income of less than twenty thousand dollars shall be allowed an additional deduction of five hundred dollars for himself or herself and an additional five hundred dollars for his or her spouse if he or she is entitled to a deduction for such personal exemptions for federal income tax purposes, provided that the exemption amount as defined under 26 U.S.C. Section 151 is not zero, and his or her spouse's Missouri adjusted gross income is less than twenty thousand dollars.
§ 143.151, RSMo