Colorado IFTA Tax Rate — 2026

How Colorado IFTA tax is calculated

For every gallon of diesel your truck "burned" inside Colorado during the quarter, you owe $0.3250 in IFTA tax. The number of taxable gallons isn't the gallons you bought there — it's the miles you drove inside Colorado divided by your fleet's average miles-per-gallon for the whole quarter.

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

Common Colorado IFTA filing questions

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

Colorado IFTA filing deadlines

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

• 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.