§ 143.071 RSMo — Corporations — inapplicable to out-of-state businesses, when

1. For all tax years beginning before September 1, 1993, a tax is hereby imposed upon the Missouri taxable income of corporations in an amount equal to five percent of Missouri taxable income.

2. For all tax years beginning on or after September 1, 1993, and ending on or before December 31, 2019, a tax is hereby imposed upon the Missouri taxable income of corporations in an amount equal to six and one-fourth percent of Missouri taxable income.

3. For all tax years beginning on or after January 1, 2020, a tax is hereby imposed upon the Missouri taxable income of corporations in an amount equal to four percent of Missouri taxable income.

4. The provisions of this section shall not apply to out-of-state businesses operating under sections 190.270 to 190.285 .