IFTA Calculator – Tax Owed vs Credit by State

Owner-operator's guide to IFTA

IFTA looks complicated but does one fair thing: it redistributes the fuel tax you already paid at the pump to the states where you actually drove. Buy cheap fuel in Texas but run miles in California, and you will owe California the difference. Buy expensive fuel where you drove, and you earn a credit. The calculator above runs the official math — fleet MPG, taxable gallons, owed vs. credit — state by state.

The formula in plain English

Fleet MPG = total miles ÷ total gallons for the quarter. Taxable gallons per state = that state's miles ÷ fleet MPG. Owed per state = (taxable − gallons bought there) × that state's rate. Add every state: positive is owed, negative is credit. Export CSV keeps the audit trail your base state wants.

Rates change quarterly — verify before filing

Prefilled rates are samples only. States adjust fuel tax rates quarterly. Always confirm the current quarter at your base-state IFTA portal (or iftach.org) before filing — the rate fields above are editable for exactly this reason. Filing with a stale rate is the most common DIY penalty.

Avoid the three classic mistakes

1) Using dashboard MPG instead of quarter actuals. 2) Mixing reefer fuel into propulsion gallons — reefer fuel is generally not IFTA-taxable, track it separately. 3) Skipping zero-mile quarters — you must still file. Keep ELD mileage logs plus every fuel receipt by state, and reconcile against your cost per mile fuel numbers monthly so quarter-end is copy-paste.

Worked example: cheap fuel state vs high-tax miles

Quarter totals: 5,200 miles (TX 3,200, CA 1,100, IL 900), 820 gallons bought. Fleet MPG = 5,200 ÷ 820 = 6.34. Taxable gallons: TX 3,200 ÷ 6.34 = 504.7, CA 1,100 ÷ 6.34 = 173.5, IL 900 ÷ 6.34 = 141.9. At sample rates TX $0.20, CA $0.979, IL $0.738, with gallons bought TX 480, CA 200, IL 140: TX owes (504.7 − 480) × $0.20 = $4.94, CA gets credit (173.5 − 200) × $0.979 = −$25.95, IL owes (141.9 − 140) × $0.738 = $1.40. Net: −$19.61 credit. Buy where you drive and credits follow; chase cheap pump price across state lines and you pay it back here.

Surcharges and gotchas: KY, VA, IN, OR

Kentucky (10.5¢) and Virginia (14.3¢) add a surcharge on gallons burned there that is always owed, never a credit — the calculator handles this when you enter KY/VA miles. Indiana folds its surcharge into the base rate, so one rate covers it. Oregon charges $0 IFTA and runs a separate weight-mile tax. Always pull the current quarter matrix from your base-state portal or iftach.org — the rate fields above are editable because states change them quarterly, and filing a stale rate is the most common DIY penalty.

What records you need for a defensible return

Keep the quarter's odometer or ELD mileage report, fuel receipts, fuel-card statements, state-by-state miles, and any records for reefer or auxiliary fuel. Receipts should identify the vehicle, date, location, gallons, and fuel type. A card statement alone may show the purchase but not every field your base state expects. Store digital copies by quarter and reconcile them before entering the final numbers. If a receipt is missing, reconstruct the purchase from the card statement and route records, then keep a note explaining the estimate.

Use one consistent fleet MPG for the quarter. Do not improve the number by excluding short trips, personal miles, or a fuel purchase that is inconvenient to categorize. If you operate multiple vehicles or fuel types, follow the rules for your base jurisdiction and keep the calculation separated where required. A clean audit trail matters more than making the return look favorable.

How to review the result before filing

First, compare the calculator's total miles with your ELD or trip reports. Second, compare total gallons with fuel receipts and the truck's expected MPG. Third, inspect every state with a large owed amount or credit: it can indicate missing fuel purchases, a mistyped rate, or miles entered under the wrong state code. Fourth, confirm the quarter and due date. Finally, export the CSV and print the filing worksheet below — retain both with the source records. To skip typing, import an ELD mileage export (jurisdiction + distance columns) with Import CSV; same-state rows merge, and the optional Unit column keeps multi-truck records separated. The result is an estimate and filing aid, not a substitute for the form or your base-state instructions.

A negative result means the entered tax-paid fuel exceeds the calculated tax obligation and may represent a credit; it does not mean every state individually refunds cash. A positive result means the calculated tax due is greater than the tax paid in the jurisdictions entered. State rules, rounding, surcharges, and filing systems can change, so verify the current matrix before submission. The IFTA filing walkthrough covers the quarter-end sequence, while the ELD comparison explains which mileage reports can reduce manual entry.

By Srikanth M. · Independent, no login, formulas shown. Last reviewed October 2026. Estimates only, not tax advice — verify rates with your base state before filing. Step-by-step: how to file IFTA · about.