Montana IFTA Tax Rate — 2026

How Montana IFTA tax is calculated

For every gallon of diesel your truck "burned" inside Montana during the quarter, you owe $0.2975 in IFTA tax. The number of taxable gallons isn't the gallons you bought there — it's the miles you drove inside Montana divided by your fleet's average miles-per-gallon for the whole quarter.

Your IFTA return then nets that against the Montana fuel-tax you already paid at the pump on gallons purchased inside the state. If you ran more Montana miles than you bought Montana fuel, you owe the difference. If you bought more Montana fuel than you ran Montana miles, you get a refund or credit.

Common Montana IFTA filing questions

• Do I file IFTA in Montana if my home base is here? If your IFTA base jurisdiction is Montana, you file your quarterly return with the Montana Department of Revenue (or equivalent). Your filing covers every IFTA jurisdiction you ran in, not just Montana.
• What if I only drove a few miles through Montana? Every IFTA mile counts, even if you only crossed the state. Track them on your trip sheet or ELD report — you'll owe (or get refunded) Montana's share whether you bought fuel here or not.
• What if Montana fuel is cheaper than the IFTA tax? The IFTA rate above is what you owe per gallon "consumed" in Montana. The pump price already includes Montana's state fuel tax — that's what gets credited on your return. If you bought all your fuel in a low-tax state and drove all your miles in Montana, you'll owe the full Montana rate on those gallons at filing time.

Montana IFTA filing deadlines

IFTA returns are due quarterly across all 48 contiguous U.S. states, including Montana:

• Q1 (Jan–Mar): due April 30
• Q2 (Apr–Jun): due July 31
• Q3 (Jul–Sep): due October 31
• Q4 (Oct–Dec): due January 31

Late filings collect penalties even if you owe nothing — some states charge $50 minimum per late return. File on time even if your net due is $0.