Revise income tax brackets to lower income taxes

This Montana bill revises state income tax brackets to lower taxes by increasing the income thresholds at which higher tax rates apply. It directly affects all Montana taxpayers, including married couples, single filers, heads of households, and estates or trusts. The key change expands the income range taxed at the lower 4.7% rate while raising the threshold for the 5.9% rate, with similar adjustments made for net long-term capital gains. The bill also updates the inflation adjustment mechanism and applies changes retroactively to tax years beginning after December 31, 2024.