Illinois IFTA Tax Rate — 2026

How Illinois IFTA tax is calculated

For every gallon of diesel your truck "burned" inside Illinois during the quarter, you owe $0.7380 in IFTA tax. The number of taxable gallons isn't the gallons you bought there — it's the miles you drove inside Illinois divided by your fleet's average miles-per-gallon for the whole quarter.

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

Common Illinois IFTA filing questions

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

Illinois IFTA filing deadlines

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

• 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.