Connecticut IFTA Tax Rate — 2026

How Connecticut IFTA tax is calculated

For every gallon of diesel your truck "burned" inside Connecticut during the quarter, you owe $0.4890 in IFTA tax. The number of taxable gallons isn't the gallons you bought there — it's the miles you drove inside Connecticut divided by your fleet's average miles-per-gallon for the whole quarter.

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

Common Connecticut IFTA filing questions

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

Connecticut IFTA filing deadlines

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

• 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.