Fuel tax credit calculator
Diesel burned by a reefer, APU or generator is taxed at the pump like road fuel, and the federal share comes back as a credit of $0.243 per gallon on IRS Form 4136. Enter the gallons to see the estimate, add your IFTA quarter to see the state net, and check which state refund programs apply.
Filled with example values — replace them with your own numbers.
Estimate only. The federal credit uses the IRS Form 4136 rates; whether your gallons qualify and how the credit is reported is for your CPA to confirm.
- Estimated federal fuel tax credit (this period)
- $138.51
- IFTA net for the quarter
- $140.00 refund
- Diesel: 570 gal × $0.243
- $138.51
- Gasoline × $0.183
- —
- LUST tax not refunded ($0.001/gal)
- $0.57
- How to claim
- Under $750.00: yearly on Form 4136 with the tax return
This is an estimate, not tax advice. It applies the published IRS rates to the gallons you enter; whether the gallons qualify, how you document them and where the credit goes on your return is for your CPA to confirm.
How the federal credit is calculated
- Federal excise tax on undyed diesel = $0.244 per gallon, of which $0.001 is the LUST (Leaking Underground Storage Tank) tax (Publication 510).
- Credit for diesel used in a nontaxable use = gallons × $0.243 (Form 4136 2025, line 3a). The LUST cent is generally not refunded, which is why the credit is $0.243 and not $0.244.
- Credit for gasoline in off-highway business use = gallons × $0.183 (Form 4136 line 1a).
- Claim: on Form 4136 with the yearly income tax return, or, when a quarter’s claim is at least $750, as a quarterly refund on Schedule 1 of Form 8849.
Which gallons qualify
The IRS calls it off-highway business use: fuel used in a trade or business other than as fuel in a highway vehicle registered for the road. For a trucking company the qualifying gallons are the ones burned by a separate engine:
- Reefer units with their own diesel engine. Publication 510 names refrigeration units as an example of special equipment run by a separate motor.
- Auxiliary power units and generators with their own engine.
- Off-road equipment such as a yard tractor or loader that is not registered for the highway.
What does not qualify: anything the truck’s own engine burns. Publication 510 says off-highway business use does not include fuel used in the propulsion motor of a registered highway vehicle even when that motor also runs equipment through a power take-off, so PTO work, idling and bunk heaters that draw on the main engine are out. If the reefer or APU shares the truck’s tank, you must apportion: a reasonable estimate from your operating experience supported by records, for example reefer run hours times the unit’s burn rate, or total fuel minus what the miles and idling used.
IFTA net credit or refund
IFTA is the state side. Each quarter the return charges every state’s diesel tax on the gallons you burned there (miles ÷ fleet MPG) and credits the state tax you already paid at the pump there. When the pump credit across all states is bigger than the tax due, the net is negative and your base state refunds it or carries a credit. That happens when you fuel mostly in high-tax states and drive mostly in low-tax ones: in Q4 2026 state diesel rates run from $0.19 in Oklahoma to $0.979 in California (full table). The IFTA calculator works out the tax due and the credit by state; drop the two totals into the IFTA fields above.
Two things keep the two credits apart. First, IFTA only covers fuel that propels the truck. Gallons pumped into a separate reefer tank are not IFTA fuel, so they do not go on the return as tax-paid purchases; listing them inflates the credit and is a common audit finding. Second, the federal credit above is on the federal $0.244; the state tax paid on reefer gallons is refunded, where it is refunded at all, by the state’s own program below.
State diesel tax refund programs
These are the programs we verified on the state’s own site on November 7, 2026. Other states have programs of their own, and the rules change; start with your state’s department of revenue.
- California: Diesel fuel tax refund for nontaxable uses, including reefer units: CDTFA says fuel consumed to operate reefer units is a nontaxable use. You need a diesel user (DU) account first and file form CDTFA-770-DU; a separate reefer tank needs its own fuel documentation. CDTFA: Diesel user claim for refund.
- Texas: The general off-highway diesel refund expired in 2005, but a refund for diesel used on or after September 1, 2025 in power take-off or auxiliary power units on a motor vehicle is available (air conditioning and heating systems are not PTO). Unlicensed claimants file Form 06-106 within the statute of limitations, which runs from the first day of the month after purchase or use. Texas Comptroller: Motor fuels tax refunds.
- Florida: Refund of tax on undyed diesel used for off-road or other exempt purposes, for entities that purchased and used tax-paid fuel for an exempt purpose. The Department of Revenue page lists the categories and links the application forms. Florida Department of Revenue: Fuel tax refunds.
Records to keep
- Fuel receipts showing the gallons, date, seller and that the diesel was undyed and tax-paid.
- Reefer or APU run hours and the unit’s burn rate, or separate-tank fill records, for the apportionment.
- The IFTA return and the state miles and gallons behind it, for the quarter.
- Copies of every Form 4136 or 8849 claim and the state refund claims filed.
The credit is one line of the year; the owner-operator taxes guide covers the rest, and the expenses list shows which fuel costs are deductible. For the quarterly state return, see how to calculate IFTA and the IFTA rates by state.
Frequently asked questions
What is the federal fuel tax credit for truckers?
The federal excise tax on undyed diesel is $0.244 per gallon (IRS Publication 510). When tax-paid diesel is used in a nontaxable use, such as a separate engine on a reefer unit, APU or generator, the IRS gives the tax back as a credit of $0.243 per gallon on Form 4136 (line 3a). The missing $0.001 is the LUST tax, which is generally not refunded.
Does reefer fuel qualify for the fuel tax credit?
Yes, when the refrigeration unit has its own engine. Publication 510 says off-highway business use includes fuel used in a separate motor to operate special equipment, and lists refrigeration units as an example. If the reefer draws from the same tank as the truck's engine, you have to work out the reefer's share with a reasonable estimate supported by your records (reefer hours and burn rate, or total fuel minus what the miles and idling used).
Does PTO or idling fuel qualify?
No. Fuel burned by the truck's own propulsion engine does not count, even when that engine runs equipment through a power take-off (Publication 510 uses a concrete mixer as the example). Idling at a dock is the propulsion engine too. An APU with its own engine does count.
How do I claim the credit: Form 4136 or Form 8849?
Form 4136 goes with your income tax return once a year and has no minimum. If your claim for a quarter reaches $750, or you can aggregate quarters of the same tax year to reach it, you can instead file Schedule 1 of Form 8849 for a refund during the quarter after the last quarter in the claim. Only one claim per quarter, and gallons refunded on Form 8849 are not claimed again on Form 4136.
Is the fuel tax credit taxable income?
If you deducted the full fuel cost, excise tax included, as a business expense, the Form 4136 instructions say to include the credit or refund in gross income. In practice the credit is still worth having; your tax preparer handles the income side.
How is an IFTA refund different?
IFTA is state tax, not federal. Each quarter the return charges each state's tax on the gallons you burned there and credits the state tax you paid at the pump there. When the pump credit across all states is bigger than the tax due, your base state sends a refund or carries a credit. Reefer gallons that go into a separate reefer tank are not propulsion fuel and do not belong on the IFTA return as tax-paid purchases; state refunds for that fuel come from the state's own refund program instead.
Which states refund diesel tax for reefer or off-road use?
Several do, each with its own form and rules. California lists reefer fuel as a nontaxable use (CDTFA-770-DU with a diesel user account). Texas refunds diesel used in power take-off or auxiliary power units since September 1, 2025 (Form 06-106), though its general off-highway refund expired in 2005. Florida refunds tax on undyed diesel used off-road or for other exempt purposes. Check your state's department of revenue for the current program.
Sources
Every rate and rule on this page was checked against these documents on November 7, 2026.
- IRS Publication 510, Excise Taxes (Rev. December 2025) — the $0.244 diesel rate, the LUST tax, the definition of off-highway business use, the refrigeration unit example, the same-tank apportionment rule and the power take-off exclusion.
- IRS Form 4136 (2025), Credit for Federal Tax Paid on Fuels — line 3a undyed diesel nontaxable use at $0.243, line 1a gasoline off-highway business use at $0.183.
- Instructions for Form 4136 (2025) — including the credit in gross income when the fuel cost was deducted.
- Schedule 1 (Form 8849), Nontaxable Use of Fuels — the $750 quarterly minimum, aggregating quarters and the filing window.
- CDTFA: Diesel user claim for refund
- Texas Comptroller: Motor fuels tax refunds
- Florida Department of Revenue: Fuel tax refunds
freightline keeps the gallons behind the claim
Fuel-card imports and receipts land on each truck, reefer fuel is tagged separately from propulsion fuel, and the IFTA quarter is built from ELD miles, so the numbers for Form 4136 and the state return come from the same place. Try it on your own trucks free for 30 days, no credit card.
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