IFTA fuel tax calculator
Enter the miles you drove and the tax-paid gallons you bought in each jurisdiction this quarter. We compute fleet MPG, taxable gallons, and the net tax or credit for each jurisdiction using the official 3Q2026 IFTA tax matrix.
| Jurisdiction | Miles | Tax-paid gallons | |
|---|---|---|---|
Estimated net due: $14.54 (fleet MPG 5.56)
| Jurisdiction | Taxable gal | Net taxable gal | Rate | Tax | Surcharge | Due |
|---|---|---|---|---|---|---|
| Texas | 539.57 | -60.43 | $0.2000 | -$12.09 | $0.00 | -$12.09 |
| Oklahoma | 179.86 | 179.86 | $0.1900 | $34.17 | $0.00 | $34.17 |
| Kentucky | 179.86 | -120.14 | $0.2200 | -$26.43 | $18.89 | -$7.54 |
Uses 3Q2026 rates from the official IFTA tax matrix (retrieved 2026-10-27). Interest and penalties are not included. Estimate only.
How the estimate works
- Fleet MPG = total miles ÷ total gallons (rounded to 2 decimals).
- Taxable gallons in each jurisdiction = miles there ÷ fleet MPG.
- Net taxable gallons = taxable gallons − tax-paid gallons bought there. Multiply by the jurisdiction's rate; negative values are credits.
- Surcharges (for diesel in 3Q2026: Kentucky and Virginia) apply to all taxable gallons with no credit for fuel bought there.
Frequently asked questions
Who has to file an IFTA return?
Carriers operating a qualified motor vehicle in two or more IFTA jurisdictions. A qualified motor vehicle has two axles and a gross or registered gross weight over 26,000 lb, or three or more axles at any weight, or is used in a combination over 26,000 lb. Your base jurisdiction issues the license and decals.
When are IFTA returns due?
The last day of the month after each quarter ends: April 30 (Q1), July 31 (Q2), October 31 (Q3) and January 31 (Q4). Late returns can draw penalties and interest, and a return is required even for a quarter with no miles.
Why do I owe a surcharge even when I bought fuel in that state?
For diesel in 3Q2026, Kentucky and Virginia charge a surcharge on every taxable gallon used there. Fuel you bought in the state does not earn a credit against the surcharge, only against the regular rate. This calculator applies the surcharge from the official matrix automatically.
Where do the rates come from?
From the official IFTA, Inc. 3Q2026 tax matrix, retrieved 2026-10-27. Rates change every quarter, so always confirm against the matrix and your base jurisdiction before filing.