How to estimate your IFTA return
- Pick the quarter. Open the official IFTA tax rate matrix for that quarter.
- Add one line per state: miles driven there, tax-paid gallons you bought there, and that state's diesel rate from the matrix.
- Add miles driven outside IFTA states, if any.
- Check what you owe or get back per state, then copy or save the PDF to compare with your return.
How it's calculated
Taxable gallons (state) = miles in that state ÷ fleet MPG
Tax due (state) = taxable gallons × state rate
Tax already paid (state) = gallons bought there × state rate
Net (state) = tax due − tax paid → positive = you owe, negative = credit
Net IFTA = sum of all states
Example (example rates, not real rates)
A truck drives 2,500 miles and buys 400 gallons, so fleet MPG is 6.25.
| State | Miles | Gallons bought | Rate | Taxable gal | Net |
|---|---|---|---|---|---|
| State A | 1,250 | 250 | $0.200 | 200 | −$10.00 credit |
| State B | 750 | 0 | $0.190 | 120 | $22.80 owed |
| State C | 500 | 150 | $0.285 | 80 | −$19.95 credit |
Net IFTA: −$10.00 + $22.80 − $19.95 = −$7.15, a small credit overall. You still owe State B $22.80; credits in other states offset it on the return.
Limitations
- This is an estimate to check your numbers. File your return through your base jurisdiction, which may round MPG and gallons differently.
- Surcharges and split-quarter rates need separate calculations and are excluded from this standard estimate. Do not add a surcharge to the regular tax rate; use your base jurisdiction's instructions.
- Covers the 48 U.S. IFTA states in U.S. dollars and gallons. Canadian provinces (liters, Canadian dollars) are not included.
- No interest or late penalties are calculated.
Related: estimate diesel cost per trip with the Fuel Cost Calculator, or see profit after fuel with the Load Profit Calculator. All formulas: How TruckingDesk calculates.
Questions
What is IFTA?
The International Fuel Tax Agreement lets interstate carriers file one quarterly fuel tax return with their base state instead of a return in every state. The return splits fuel tax between states by the miles driven in each.
Who has to file IFTA?
Carriers running qualified motor vehicles across state lines: vehicles with two axles and a gross or registered weight over 26,000 pounds, three or more axles regardless of weight, or a combination over 26,000 pounds. Check with your base jurisdiction if you're unsure.
When are IFTA returns due?
Quarterly, on the last day of the month after the quarter ends: April 30, July 31, October 31 and January 31. If a due date falls on a weekend or holiday, check your base jurisdiction's rules.
How do I calculate IFTA fuel tax by state?
Divide total miles by total gallons to get fleet MPG. For each state, divide its miles by that MPG to get taxable gallons, multiply by the state rate, and subtract the tax you already paid on fuel bought there.
Why doesn't TruckingDesk fill in the tax rates?
Rates change quarterly and some states use surcharges or split rates. Using an old rate would give a wrong answer, so you copy the current rates from the official IFTA matrix.
Is my data saved or sent anywhere?
No. The math runs in your browser. Only if you tick the remember box are the tax rates you typed saved on this device.