Upon voter approval, this constitutional amendment repeals Sections 4(d) and 26 of Article X of the Missouri Constitution and adopts two new sections in their place relating to taxation. The amendment authorizes the General Assembly, when enacting any law imposing a tax measured by income, to define income by reference to provisions of federal law as those provisions may become effective from time to time, whether retrospective or prospective. The General Assembly must set the rate or rates of any such tax and may make exceptions, additions, or modifications to any federal provisions referenced in defining income. The amendment establishes a mechanism to reduce and eliminate the state individual income tax based on increases in net general revenue collections. For a calendar year, the rate of the individual income tax must be reduced by one-hundredth of one percent if net general revenue collections in the previous fiscal year exceed by at least $20 million the amount of net general revenue collections for the fiscal year ending June 30, 2025. The amount of net general revenue collections for the fiscal year ending June 30, 2025, must be adjusted annually by the rate of inflation. If the minimum amount of net general revenue collections required to trigger a reduction is met, each additional increase in net general revenue collections in the previous fiscal year by $20 million beyond that minimum must result in an additional reduction of one-hundredth of one percent, up to a maximum reduction of one and six-tenths percent in a calendar year. If the rate reductions required under the amendment would cause the individual income tax rate to fall below one and four-tenths percent for any tax year, the rate imposed must instead be 0%. If the reductions do not eliminate the individual income tax by January 1, 2032, the tax may continue until it is eliminated according to the revenue triggers and rate reductions established in the amendment. For any tax year beginning on or after the date the individual income tax rate has been reduced to 0%, no individual income tax may be enacted or imposed by the state. The amendment specifies that elimination of the tax does not affect the collectability of liabilities or debts for tax years beginning before the date of elimination and does not apply to an earnings tax or similar tax imposed by a political subdivision. For purposes of this provision, "individual income tax" is defined as the tax imposed on the income of natural persons under Sections 143.011 and 143.041, RSMo.