Estimate your quarterly IFTA fuel tax by jurisdiction from your miles, gallons purchased and each state's tax rate.
How IFTA works
The International Fuel Tax Agreement lets interstate carriers file a single quarterly fuel tax return with their base jurisdiction instead of separate returns in every state and province they cross. Tax is owed to each jurisdiction based on the fuel you burned there (your miles in that jurisdiction divided by your fleet MPG), and you get credit for tax already paid at the pump on gallons purchased there. The difference nets out across all jurisdictions into a single payment or refund.
Using this calculator
Enter your total miles and total gallons for the quarter to establish your fleet MPG, then add a row for each jurisdiction with the miles you ran there, that jurisdiction's diesel tax rate per gallon, and the gallons you purchased there. The calculator computes taxable gallons, tax due and purchase credits per jurisdiction and nets them into your estimated quarterly position. Rates change quarterly, so take the current rate for each jurisdiction from the official IFTA rate tables linked below when filing.
Records and tips
IFTA audits come down to mileage records, so keep per-jurisdiction distance data from your ELD or GPS system and retain fuel receipts showing gallons and location. Buying fuel in low-tax states does not reduce what you owe (tax follows where you burn fuel, not where you buy it), but pump price net of tax does vary, which is where fuel cards and price shopping genuinely save money.
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