Idaho IFTA Tax Rate — 2026

How Idaho IFTA tax is calculated

For every gallon of diesel your truck "burned" inside Idaho during the quarter, you owe $0.3200 in IFTA tax. The number of taxable gallons isn't the gallons you bought there — it's the miles you drove inside Idaho divided by your fleet's average miles-per-gallon for the whole quarter.

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

Common Idaho IFTA filing questions

• Do I file IFTA in Idaho if my home base is here? If your IFTA base jurisdiction is Idaho, you file your quarterly return with the Idaho Department of Revenue (or equivalent). Your filing covers every IFTA jurisdiction you ran in, not just Idaho.
• What if I only drove a few miles through Idaho? 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) Idaho's share whether you bought fuel here or not.
• What if Idaho fuel is cheaper than the IFTA tax? The IFTA rate above is what you owe per gallon "consumed" in Idaho. The pump price already includes Idaho'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 Idaho, you'll owe the full Idaho rate on those gallons at filing time.

Idaho IFTA filing deadlines

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

• 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.