How we calculate this
- Fleet MPG = total miles ÷ total gallons bought (2 decimals)
- Taxable gallons (state) = miles in that state ÷ fleet MPG
- Tax due (state) = taxable gallons × state rate
- Tax paid (state) = gallons bought in that state × state rate
- Net (state) = tax due − tax paid (positive = you owe, negative = credit)
- Net IFTA tax = sum of every state's net
Surcharges some states add, Canadian provinces and rounding rules differ by base state, so treat the result as an estimate and check it against your base state's return.
Worked example
10,000 miles on 1,600 gallons is 6.25 MPG. Using round example rates (not real ones): 5,000 Texas miles, 1,200 gallons bought there at $0.20; 3,000 Oklahoma miles, 400 gallons at $0.19; 2,000 Arkansas miles, no fuel, at $0.285.
| State | Taxable gal | Net |
|---|---|---|
| TX | 800 | credit $80.00 |
| OK | 480 | owe $15.20 |
| AR | 320 | owe $91.20 |
Net for the quarter: you owe $26.40. Buying fuel where the rate is low and driving where it's high is why most drivers owe a little each quarter.
FAQ
How is IFTA tax calculated?
Divide your total miles in all jurisdictions by the total gallons you bought to get fleet MPG. For each state, divide the miles you drove there by your MPG to get taxable gallons, multiply by that state's rate, then subtract the tax you already paid at the pump on gallons bought there. A positive result is what you owe that state; a negative one is a credit.
When is the IFTA return due?
The last day of the month after each quarter: April 30, July 31, October 31 and January 31. You file even if you didn't drive that quarter.
What happens if I file IFTA late?
The penalty is $50 or 10% of the net tax due, whichever is greater, plus interest. Repeated late filing can get your IFTA license revoked.
Where do I get the IFTA tax rates?
IFTA, Inc. publishes every jurisdiction's rate for each quarter in its tax rate matrix at iftach.org. Some states add a surcharge on a separate line. This calculator fills in each state's diesel rate (surcharge included) from that matrix for the quarter you pick, and our IFTA fuel tax rates page lists them all. You can type over any rate.
Who needs to file IFTA?
Carriers running a qualified motor vehicle in two or more member jurisdictions: two axles and over 26,000 lbs, three or more axles, or a combination over 26,000 lbs. Your base state issues the license and you file one return there.
Is my information saved or shared?
Your entries are saved only in your own browser. Nothing is sent to Trucking Help Center, and there's no signup. If you log fuel receipts in TruckMate on the same browser, one tap fills in the gallons per state.