This free IFTA calculator works the way the quarterly return does: total miles and total gallons give your fleet MPG, miles in each jurisdiction divided by that MPG give taxable gallons, and the difference between taxable gallons and the gallons you bought there, times that jurisdiction's rate, is what you owe or get credited. Add a row for every state or province you ran in during the quarter.
IFTA fuel tax calculator
How IFTA works
The International Fuel Tax Agreement lets you hold one fuel tax license from your base state and file one quarterly return instead of dealing with every state you drove through. It applies to qualified motor vehicles used across state lines: anything over 26,000 pounds gross vehicle weight, anything with three or more axles regardless of weight, or a combination over 26,000 pounds. Your base state issues the license and two decals per truck and settles up with the other states on your behalf.
The tax itself is owed where you burn fuel, not where you buy it. You already pay each state's tax at the pump. The return reconciles the two: if you bought 150 gallons in Texas but burned 200 gallons of Texas miles, you owe Texas tax on 50 gallons. If you bought more than you burned, that state owes you a credit, and the credits offset what you owe elsewhere. The math, in the order the calculator does it:
- Total miles in all jurisdictions ÷ total gallons purchased = fleet MPG (rounded to two decimals).
- Miles in a jurisdiction ÷ fleet MPG = taxable gallons for that jurisdiction.
- Taxable gallons − tax-paid gallons purchased there = net taxable gallons (negative means credit).
- Net taxable gallons × that jurisdiction's rate for the quarter = tax due or credit.
- Sum every jurisdiction. Pay the net to your base state, or take the refund.
IFTA quarterly deadlines
| Quarter | Months covered | Return and payment due |
|---|---|---|
| Q1 | January – March | April 30 |
| Q2 | April – June | July 31 |
| Q3 | July – September | October 31 |
| Q4 | October – December | January 31 |
If the due date falls on a weekend or holiday, the next business day counts. A late return costs $50 or 10% of the net tax due, whichever is greater, plus interest on each jurisdiction's balance. File even when you owe nothing, and file a zero return for a quarter the truck did not move; missing returns are what get licenses revoked, not small balances.
IFTA record-keeping requirements
You are filing a summary. An audit asks for the records behind it, and you must keep them for four years from the return's due date or filing date, whichever is later. For every trip, the distance records must show:
- Date the trip started and ended
- Origin and destination
- Route of travel
- Beginning and ending odometer or hubometer readings
- Total trip miles and miles in each jurisdiction
- Vehicle unit number and the licensee's name
If you use an ELD or GPS system for distance, its location readings need to be frequent enough to prove the miles in each state, with the raw location data retained, not just the summary. Fuel records must show the date, seller's name and address, gallons, fuel type, price, unit number, and the purchaser's name; a receipt with the amount only is not enough. Keep bulk fuel withdrawals separately. Our DOT compliance guide covers the rest of the paperwork that comes up in the same audit.
Common IFTA audit triggers
- Implausible MPG. A Class 8 tractor reporting 3 MPG or 11 MPG is the first thing an auditor sorts by. If reefer fuel or a pickup's fuel got mixed into truck gallons, the MPG gives it away.
- Fuel bought in a state with no miles reported there. You cannot fill up in Oklahoma without driving in Oklahoma.
- Round numbers. Miles by state that end in 00 every quarter look estimated, because they are.
- Odometer gaps. Trip records where one trip's ending odometer does not match the next trip's beginning.
- Miles that disagree with your IRP renewal. Both filings use the same distance records and auditors compare them.
- Late or amended returns. A pattern of either moves you up the list.
An audit without records does not end at zero. The auditor can assess tax on estimated miles at a low assumed MPG for every jurisdiction, which is nearly always worse than what you would have owed.
Where TruckFlow.ai fits with your IFTA records
Every load in TruckFlow.ai has its pickup and delivery stops on the load record. If you connect Motive or Samsara, truck location syncs in read-only, so you can see where each truck has been. Your ELD's own IFTA mileage report stays the primary distance record. The trucking dispatch software page shows how loads are built from rate cons, and owner-operator trucking software covers a one-truck setup.
IFTA calculator FAQ
Do I need IFTA for a hotshot or pickup truck?
Only if the combination exceeds 26,000 pounds gross or has three or more axles on the power unit. A one-ton pickup with a gooseneck trailer usually crosses 26,001 pounds combined and needs IFTA when it runs interstate. A truck that never leaves its home state does not.
What if I only drove in my home state this quarter?
File anyway. A return with all miles in one jurisdiction and zero net tax keeps the license active. Not filing is a $50 penalty and a step toward revocation.
Do reefer fuel and off-road fuel count?
Fuel burned in a reefer unit is not taxable under IFTA when it is bought from a separate pump and receipted separately. If reefer fuel is mixed into your tractor gallons, your MPG drops and you overpay. Keep separate receipts.
Where do the rates come from?
Each jurisdiction sets its own rate and can change it every quarter. The official source is the IFTA tax rate matrix at iftach.org. Use the diesel column for the quarter you are filing, not the current quarter.
Keep every load's stops and paperwork in one place before the quarter closes. Start a free 14-day TruckFlow trial, no credit card required. Every load carries its own stops and documents. Plans from $99/mo; see pricing. More free tools: cost per mile calculator, bill of lading template, and rate confirmation template.