You don’t need fancy software to file IFTA. An IFTA calculator only does four things: it works out your fleet MPG, splits your fuel by state based on miles, applies each state’s tax rate, and credits the fuel tax you already paid at the pump. This guide walks you through that math by hand with a full worked example, so you can check any IFTA calculator, spreadsheet or return before you file. Heads up: the Q3 2026 IFTA return is due Monday, November 2, 2026.
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When is IFTA due? (Q3 2026 IFTA calculator deadline)
IFTA returns are due on the last day of the month after each quarter ends. When that day falls on a Saturday, Sunday or legal holiday, the due date moves to the next business day (IFTA Articles of Agreement, R960).
| Quarter | Months | Usual due date |
|---|---|---|
| Q1 | Jan–Mar | April 30 |
| Q2 | Apr–Jun | July 31 |
| Q3 | Jul–Sep | October 31 (Nov 2, 2026, because Oct 31 is a Saturday) |
| Q4 | Oct–Dec | January 31 |
You have to file even if you didn’t run that quarter. A zero return is still a return. Late filing can bring a penalty of $50 or 10% of the late tax, whichever is greater, plus interest (R1220 and R1230). Your base state can add its own penalties.
Free: Know Your Number cost-per-mile calculator. See your break-even rate before you book a load.
What you need before you use an IFTA calculator
Pull these together for the quarter:
- Miles by state for each qualified vehicle, from your ELD trip reports or trip sheets. Count loaded, empty and bobtail miles alike.
- Every fuel receipt with the date, state, gallons and seller. You only get credit for tax-paid fuel you can prove with a receipt or fuel card statement (R1000).
- The current IFTA tax rates for each state you ran in, from the quarterly tax rate matrix at iftach.org. Rates change every quarter, and some states add surcharges.
A “qualified motor vehicle” for IFTA is generally one with two axles and a gross or registered weight over 26,000 pounds, three or more axles at any weight, or a combination over 26,000 pounds (R245).
How to calculate IFTA: the IFTA calculator formula
Here’s the math every IFTA calculator runs:
- Fleet MPG = total miles (all states) ÷ total gallons (all states)
- Taxable gallons for each state = miles in that state ÷ fleet MPG
- Net taxable gallons = taxable gallons − tax-paid gallons you bought in that state
- Tax due or credit = net taxable gallons × that state’s rate
- Total = add up every state. A positive total means you owe your base state. A negative total is a credit or refund.
IFTA calculator example, step by step
One truck, Q3, three states. The states and tax rates are made up for the example. Use the real rates from the IFTA matrix when you file.
Step 1: Fleet MPG – Total miles: 25,000 – Total gallons: 4,000 – Fleet MPG: 25,000 ÷ 4,000 = 6.25
Steps 2–4: Work each state
| State | Miles | Taxable gal (miles ÷ 6.25) | Gallons bought | Net taxable gal | Example rate | Tax (credit) |
|---|---|---|---|---|---|---|
| State A | 12,000 | 1,920 | 2,500 | −580 | $0.30 | ($174.00) |
| State B | 8,000 | 1,280 | 1,500 | −220 | $0.40 | ($88.00) |
| State C | 5,000 | 800 | 0 | 800 | $0.50 | $400.00 |
| Total | 25,000 | 4,000 | 4,000 | 0 | $138.00 due |
Step 5: Read the result You burned fuel in State C but didn’t buy any there, so you owe State C $400. You bought more fuel than you burned in States A and B, so you get credits of $174 and $88. Net due: $138.00, paid to your base state, which splits it among the states.
That’s why fueling in low-tax states doesn’t “save” IFTA money the way many drivers think. You pay each state for the fuel you burn there, wherever you buy it. Cheaper fuel at the pump can still lower what you spend, though, and that affects your trucking cost per mile.
Rather not do this by hand every quarter? The HaulLedger IFTA Fuel & Miles Tracker is an Excel and Google Sheets workbook. You log trip miles and fuel receipts, type in the current rates, and it adds up your fleet MPG, taxable gallons and estimated tax by state. Or keep using a calculator and the steps above.
IFTA calculator mistakes that cause audits
- Missing miles. Your total miles have to match your ELD or odometer. Gaps are the first thing an auditor looks for.
- Fuel without receipts. No receipt, no tax-paid credit.
- Last quarter’s rates. Rates change quarterly, so pull the new matrix every time.
- Mixing in reefer fuel. The return counts the fuel that goes into the truck’s own fuel tanks. If your reefer has a separate tank, keep those receipts separate.
- Tossing records. Keep your IFTA records for 4 years from the due date or the filing date, whichever is later (IFTA Procedures Manual, P510).
If you’re new to authority, IFTA is one of the yearly costs to budget in your trucking business plan.
Free: Know Your Number cost-per-mile calculator. See your break-even rate before you book a load.
IFTA calculator FAQ
How do you calculate IFTA tax? Divide total miles by total gallons for your fleet MPG. Divide each state’s miles by that MPG for taxable gallons, subtract the gallons you bought there, and multiply by the state’s rate. Add up all the states for your total due or credit.
When is the Q3 2026 IFTA return due? Monday, November 2, 2026. October 31 falls on a Saturday, so the due date moves to the next business day.
Do I have to file IFTA if I didn’t drive? Yes. IFTA returns are required even when you had no operations or no taxable fuel that quarter (R930).
What happens if I file IFTA late? Your base state can charge a penalty of $50 or 10% of the late tax, whichever is greater, plus interest, and it may suspend your license for not complying.
Where do I find IFTA tax rates? The quarterly tax rate matrix on iftach.org. Use the matrix for the quarter you’re filing.
How long do I keep IFTA records? 4 years from the return’s due date or filing date, whichever is later.
Is there a free IFTA calculator? Yes, several online calculators and spreadsheets exist, and you can do it on paper with the steps above. Any of them is only as good as the miles and receipts you put in.
Get your IFTA calculator numbers right before Nov 2
Gather your miles and receipts now, pull the Q3 2026 rate matrix, and run the five steps. If you want the math done for you every quarter, the IFTA Fuel & Miles Tracker keeps your miles, fuel and estimated IFTA in one Excel or Google Sheets file.
Not tax or legal advice. The example uses made-up states and rates. Your base jurisdiction’s rules and the current IFTA tax matrix decide what you owe. Check with your base state or a tax professional if you’re not sure.
Sources (checked October 2026)
- IFTA, Inc., Articles of Agreement (2026): R245 (qualified motor vehicle), R960 (due date), R1000 (tax-paid credit), R1220 (penalties), R1230 (interest), R930 (returns required with no operations), R420 (suspension)
- IFTA, Inc., Procedures Manual (2026): P510 (4-year record retention)
- IFTA, Inc., Tax rate matrix and Carriers page