Retiring in Montana

Every figure below is sourced to Montana’s own publications and dated. Estimates only, and not tax advice.

Retirement tax by state

What your state actually takes from a 401(k) withdrawal, a pension, and Social Security — in dollars, not a yes/no list.

Long-term index-fund growth after expense-ratio drag — and what your state takes from the gains at withdrawal.

Decided on the two rates that actually govern it — yours now, and yours at withdrawal, in the state you'll retire in rather than the one you're in.

2026 limits, employer match, the 60-63 super catch-up, and whether the Roth catch-up mandate applies to you.

When your RMDs start under SECURE 2.0, how much this year's is, and what missing it costs.

What a backdoor Roth conversion would actually cost you in tax — the pro-rata rule most calculators only describe.

The tax a leveraged rental owes inside a self-directed IRA — computed at trust rates, not the rate you'd assume.

401(k) and IRA withdrawals: Taxed
Social Security: Fully taxed
Top marginal rate: 5.65%; The top of 2 graduated brackets.
Tax year: 2026; Brackets are legislated and change on a fixed calendar, so the year matters.

MONTANA STARTS FROM FEDERAL TAXABLE INCOME, not federal AGI — federal AGI less the federal standard or itemized deduction, and expressly EXCLUDING the federal qualified business income deduction. It has no state standard deduction of its own and no personal or dependent exemptions; the figures recorded in standardDeduction are the federal amounts Montana adopts by conformity.
NOT MODELLED: a flat $5,660 subtraction for each taxpayer aged 65 or over ($11,320 where both spouses qualify) under MCA 15-30-2120(3)(g), applied on Form 2 page 1 line 6 with NO income limit. A Montana result for an older filer will therefore overstate the tax, materially so for a couple. New for 2026 and also not modelled: a $3,000 subtraction for a qualified volunteer firefighter or emergency care provider under 15-30-2120(3)(o).
The federal OBBBA below-the-line deductions — qualified tips, qualified overtime, passenger vehicle loan interest, and the enhanced senior deduction — all FLOW THROUGH to Montana taxable income, on top of Montana's own age-65 subtraction.
Montana's 2026 brackets are statutorily fixed by HB 337 and are NOT inflation-indexed; indexing resumes in 2027, when the top rate also falls to 5.4% and the thresholds rise to $65,000 single, $97,500 head-of-household and $130,000 married-joint.