The Survivor Benefit Plan offered by the federal government qualifies for the public pension exemption on your Missouri tax return, rather than the military retirement subtraction.
According to How is my annuity from the Survivor Benefit Plan taxed? in the Missouri Department of Revenue’s Military Reference Guide:
The Survivor Benefit Plan is a program offered by the United States government to retired members of the military servicemember so that upon the death of the retired servicemember, an annuity is provided to a designated person (usually the surviving spouse) as a replacement for the military retirement pension. Although the annuity does not qualify for the military retirement pension exemption for the 2020 and prior tax years or the military retirement subtraction on 2021 tax return, it does qualify for the public pension exemption on any tax year.
