Montana Gov. Greg Gianforte unveiled a proposal Tuesday to establish a single 4.7% income tax rate statewide, according to reporting by the Daily Montanan. The announcement came at an event co-hosted with the Mountain States Policy Center at the Montana Capitol in Helena on September 8, 2026.

The proposal would replace the state’s current two-bracket system, which tops out at 5.4%. Many Montanans already pay the proposed 4.7% rate—specifically, households filing jointly with taxable income up to $95,000. Since taking office in 2021, Gianforte has overseen a reduction in Montana’s income tax brackets from seven to two.

Gianforte framed the measure as beneficial for residents and employers. “It would provide certainty to Montanans as well as business owners looking to invest in our state and create jobs,” he told the Daily Montanan.

The governor’s office cited Montana’s improved fiscal standing as evidence the state’s tax approach is working. The state’s national fiscal ranking has climbed from No. 22 to No. 8 under his administration, according to Truth in Accounting. Gianforte also pointed to business relocations, including Janicki Industries, as signs the state’s tax environment is attracting investment.

Democrats and fiscal watchdog groups quickly opposed the plan. Rep. Mark Thane of Missoula, who served as vice chair of the House Taxation Committee during the 2025 legislative session, called it a giveaway to the wealthy. “This proposal is a $120 million tax break for the wealthiest income earners. If there’s one thing we have learned, it’s that trickle-down economics is a myth,” Thane told the Daily Montanan.

The Montana Budget and Policy Center also opposed the proposal. According to Democratic analysis cited in the reporting, 95% of the income tax reductions would flow to the top 20% of earners. The top 1% of income earners—those making above $900,000 annually—would receive an average tax cut of $9,000 per year.

The Legislative Fiscal Division estimated the proposal could reduce state tax collections by $130 million annually by 2029, though the governor’s office has not released its own fiscal projections.

The flat-tax proposal arrives as Republican lawmakers prepare for the 2027 legislative session. Discussion of a statewide sales tax has also circulated among state Republicans ahead of the session, though no formal proposal has emerged. Neighboring states Idaho and Wyoming have pursued flat-tax or no-income-tax models; South Dakota imposes no income tax.

Gianforte launched his flat-tax campaign earlier this year with the policy group, and has continued backing the 4.7% rate ahead of the 2027 Legislature.