The IRS has a name for promoters who sell inflated fuel tax credit claims: Dirty Dozen. In its April 2, 2024 release, IR-2024-89, the IRS warned that the fuel tax credit is available only for off-highway business and farming use, that it was seeing an increased number of fictitious claims on Form 4136, and that people who falsely claim it may face fines, prosecution and imprisonment.
That does not mean every claim is fraud. Trucking companies burn real fuel in real nontaxable uses, and the credit for it is legitimate. The trick is knowing exactly which gallons qualify and being able to prove it.
Why there is a credit at all
Federal excise tax is built into the price of highway fuel. IRS Publication 510 (December 2025) states the tax on diesel fuel and kerosene as $0.244 per gallon. The tax funds highways, so when fuel is used for a purpose the law treats as nontaxable, the Code lets the user recover the tax.
For gasoline, IRC 6421(a) provides that if gasoline is used in an off-highway business use, the IRS pays the ultimate purchaser the tax imposed on it. Under section 6421(i), most businesses take that as an income tax credit under IRC 34 rather than a direct payment. Diesel and kerosene have a parallel system for nontaxable uses, and the claims for both are made on Form 4136 with your income tax return, or on Form 8849 or Form 720 Schedule C in some cases.
What counts as off-highway business use
The statutory definition in IRC 6421(e)(2)(A) is the key: off-highway business use means use by a person in a trade or business, or an income-producing activity, otherwise than as a fuel in a highway vehicle registered or required to be registered for highway use.
Publication 510 gives examples of off-highway business use:
- Fuel used in stationary machines such as generators, compressors and power saws.
- Fuel used for cleaning purposes.
- Fuel used in forklift trucks, bulldozers and earthmovers.
The Instructions for Form 4136 make the boundary explicit for diesel: fuel used in the propulsion engine of a diesel-powered highway vehicle does not qualify. Your tractor's fuel, burned to move the tractor down the road, is the taxable use the tax is designed to hit.
The reefer unit
Here is where many trucking companies have a real claim. Publication 510 addresses fuel used in a separate motor that runs special equipment on a highway vehicle, such as a refrigeration unit, pump, generator or mixing unit. If the separate motor draws from its own tank, the fuel in that tank is fuel used off-highway. If it draws from the same tank that supplies the propulsion engine, you must figure how much went to the separate motor.
Publication 510 says you may make a reasonable estimate based on your operating experience and supported by your records. Its method: use devices that measure miles traveled, such as hubometers, to figure the fuel used to propel the vehicle, add the fuel consumed while idling or warming up before moving, and treat the difference between total fuel and propulsion fuel as fuel used in the separate motor.
The publication's example is a refrigerated truck with a separate reefer motor sharing a tank. The owner uses the hubometer to determine that 90 percent of the fuel propelled the truck, so 10 percent was used in an off-highway business use.
Notice the words "supported by your records." A flat percentage pulled from a promoter's spreadsheet is not an estimate based on your operating experience.
Mobile machinery
Some purpose-built trucks qualify under a separate rule. Section 6421(e)(2)(C) includes use in mobile machinery that meets both a design-based test and a use-based test. The design test requires a chassis with permanently mounted machinery to perform an operation such as construction, manufacturing, processing, farming, mining, drilling or timbering that is unrelated to transportation, a chassis specially designed to serve only as the mount for that machinery, and a design that could not be used to transport other loads without substantial structural modification. The use-based test requires less than 7,500 miles of public highway use during the taxable year. Ordinary freight trucks do not meet this test.
Publication 510's type-of-use table notes that, for type of use 2, the mobile machinery parenthetical applies only to Form 8849 and Form 720. Read the form instructions for the right place to claim.
What does not count
- Fuel burned in the propulsion engine of a registered highway vehicle.
- Fuel lost or destroyed by spillage, fire or other casualty. Publication 510 says you cannot treat it as fuel used in an off-highway business use.
- Personal use and commuting.
- The same gallons claimed twice. The Form 4136 instructions say you cannot claim the same amounts on more than one of Form 4136, Form 8849 and Form 720.
Who claims, and on which form
The person who can claim is generally the ultimate purchaser who used the fuel in the nontaxable use. The Form 4136 instructions describe three routes for these claims: an annual claim on Form 4136 filed with the income tax return, a periodic refund claim on Form 8849, or a claim on Form 720, Schedule C, to offset excise tax liability. You choose one route for a given amount. Claiming the same gallons on Form 4136 and again on Form 8849 is exactly the kind of excessive claim the penalty below is aimed at.
Make sure the gallons on the claim tie to fuel invoices that show the tax was actually paid. Publication 510 says only the $0.001 per gallon LUST tax applies to dyed diesel, so dyed fuel does not generate a credit for the $0.244 you never paid.
The penalty for claiming too much
IRC 6675 imposes a civil penalty on any person who makes a claim under section 6421 or 6427, among others, for an excessive amount, unless the excess was due to reasonable cause. The penalty is the greater of two times the excessive amount or $10. That is in addition to any criminal penalty.
Two times the excess. If you claim $10,000 and $8,000 was not allowable, the penalty can be $16,000 on top of repaying the $8,000. Section 6421(g)(2) also gives the IRS authority to examine books and witnesses to check the correctness of any claim, as if the claimant were the person liable for the tax.
Records that support a claim
The Form 4136 instructions say to keep records supporting the credit for at least 3 years from the date the return is due or filed, whichever is later, and to keep fuel receipts with your records rather than attaching them to the return. For a reefer or other separate-motor claim, a defensible file includes:
- Fuel purchase records by vehicle, with gallons and dates.
- Hubometer or odometer readings and the propulsion fuel computation.
- Reefer engine hour meter readings and fuel consumption data, if the unit tracks them.
- The written method you used, applied the same way every period.
- Separate tank records if the reefer has its own tank.
If you already claimed too much
If you used a preparer or promoter who produced a large fuel credit with no data behind it, do not wait for the IRS. The IRS release encouraged taxpayers to use reputable professionals and directed people to report abusive promoters on Form 14242. A corrected return or claim, filed before an examination, puts you in a different position than one the IRS finds, and the reasonable cause exception in section 6675 depends on how you acted.
Fuel credits sit alongside other trucking excise issues. See our guide to the 12 percent heavy truck tax and our Form 2290 guide. If you are facing an examination, read how the firm approaches IRS audits.
The reefer burns real fuel. Claim it with real numbers, because the penalty for guessing high is double.