The Montana gas tax is $0.33 per gallon on gasoline and $0.2975 per gallon on diesel, charged to fuel distributors and passed through to drivers at the pump.1Montana State Legislature. Montana Code 15-70-403 – Gasoline, Special Fuel, and Aviation Fuel Tax — Incidence — Rates Add the $0.0075-per-gallon petroleum storage tank cleanup fee and the federal excise tax, and the total tax on a gallon of regular gasoline lands near $0.52; diesel runs about $0.55. Montana has no general sales tax, so nothing extra gets tacked on at the register.
Current State Fuel Tax Rates
Montana sets its fuel tax rates by statute, per gallon distributed within the state:
- Gasoline: $0.33 per gallon
- Special fuel (diesel and biodiesel): $0.2975 per gallon
- Aviation fuel: $0.05 per gallon, excluding fuel sold to the federal defense fuel supply center
These rates don’t adjust for inflation. Any change has to come through the legislature, which is why the gasoline rate has held at $0.33 since July 1, 2022.1Montana State Legislature. Montana Code 15-70-403 – Gasoline, Special Fuel, and Aviation Fuel Tax — Incidence — Rates
The Petroleum Storage Tank Cleanup Fee
On top of the excise tax, distributors owe a $0.0075-per-gallon fee on gasoline, aviation gasoline, special fuel, and heating oil. It funds cleanup of contaminated petroleum storage tank sites.2Montana State Legislature. Montana Code 75-11-314 – Petroleum Storage Tank Cleanup Fee — Collection — Penalties — Warrant for Distraint — Statute of Limitations The fee suspends whenever the cleanup fund’s unobligated balance reaches $10 million and turns back on when it drops below $6 million, so it cycles. When active, the combined state charge is $0.3375 on gasoline and $0.305 on diesel.
What Federal Tax Adds
Every gallon sold in Montana also carries a federal excise tax: $0.184 for gasoline and $0.244 for diesel. Both figures include a $0.001-per-gallon surcharge for the Leaking Underground Storage Tank Trust Fund.3Office of the Law Revision Counsel. 26 USC 4081 – Imposition of Tax That per-gallon load is the whole tax bill; there is no percentage-based sales tax layered on top.
Where the Money Goes
Fuel tax revenue bypasses the general fund. Of the $0.33 gasoline tax, 22 cents goes to the highway restricted account for state road work, 4 cents to highway patrol administration, and 7 cents to a local government road construction and maintenance account.1Montana State Legislature. Montana Code 15-70-403 – Gasoline, Special Fuel, and Aviation Fuel Tax — Incidence — Rates
Diesel splits differently. Out of the $0.2975 special fuel tax, 24.6 cents goes to the highway restricted account, 4 cents to highway patrol, and 1.15 cents to local governments. The local share is smaller for diesel, but the total volume distributed for agriculture and freight makes the account meaningful.
Refunds for Off-Road Fuel Use
If you buy taxed gasoline or clear diesel and burn it off the highway, in farm equipment, generators, boats, or similar uses, you can claim back the Montana fuel tax. The refund runs through the Montana Department of Transportation, not the Department of Revenue.
The 36-Month Deadline
You have 36 months from the purchase date on your invoice to file a refund claim.4Montana State Legislature. Montana Code 15-70-432 – Application for Refund or Credit — Filing — Correction by Department Miss the window and the claim is dead, no matter how well-documented.
What Documentation You Need
Your application must include the original bulk delivery invoice or an electronic transaction report showing the dealer’s name and location, the date of purchase, the type and quantity of fuel, and proof that Montana fuel tax was paid. A receipt missing any of those elements will not support a refund. Engine-hour or mileage logs for the off-road equipment help justify the gallons you’re claiming.
Electronic filing through the Department of Transportation’s online portal doesn’t require you to submit original invoices, but you still have to keep them. Paper filings go to the Motor Carrier Services Division at MDT in Helena with the original invoices attached. If the department finds non-fraudulent errors, it can correct the claim and approve the corrected version or ask you to amend.
Federal Refund Is Separate
Off-road users may also qualify for a federal excise tax refund on IRS Form 8849, Schedule 1.5Internal Revenue Service. About Form 8849, Claim for Refund of Excise Taxes The state and federal claims are two separate filings to two separate agencies. Qualifying for one does not carry you across to the other.
Dyed Diesel Rules
Diesel meant for off-road use is dyed at the refinery or terminal and never has state fuel tax applied to it in the first place.1Montana State Legislature. Montana Code 15-70-403 – Gasoline, Special Fuel, and Aviation Fuel Tax — Incidence — Rates Running dyed diesel in a vehicle on public roads is illegal.
Montana’s civil penalties start at up to $1,000 for a first offense and up to $5,000 for a second, with each use of dyed fuel on the highway counted separately. A third or later offense becomes criminal. The operator owes the unpaid tax, and the seller can be held jointly liable if the seller knew or should have known the fuel would go on-road.6Montana Code Annotated. Montana Code 15-70-441 – Dyed Special Fuel Restrictions — Penalties Federal penalties stack on top: the IRS can assess the greater of $1,000 or $10 per gallon found in the tank at inspection, escalating from there.
IFTA for Interstate Carriers
Commercial carriers who cross state lines with vehicles over 26,000 pounds gross weight, or with three or more axles regardless of weight, register under the International Fuel Tax Agreement. Montana runs the program through MDT’s Motor Carrier Services division.7Montana Department of Transportation. IFTA Guidelines
One IFTA license covers your whole fleet and runs from January 1 through December 31. Each truck displays decals on both sides of the cab. Operating without decals or a copy of the license can trigger a citation or force you to buy a fuel trip permit on the spot.
Quarterly returns reconcile fuel bought in each state against miles driven in each state. Deadlines fall on April 30, July 31, October 31, and January 31. Late filing or underpayment triggers a penalty of $50 or 10 percent of the net tax liability, whichever is greater, plus interest. Carriers who haven’t filed everything and paid what they owe can’t renew their IFTA credentials.
Records are where IFTA audits usually turn painful. You have to keep fuel receipts and distance records for four years after the return was due or filed. Receipts need the date, seller name and address, quantity, fuel type, price, and the vehicle fueled. Credit card statements alone won’t do it.
Electric Vehicles Pay a Registration Fee Instead
EVs don’t buy taxed fuel, so Montana collects an annual registration fee that scales by vehicle weight:
- Class 1 (under 6,000 lbs): $130 for full EVs, $70 for plug-in hybrids
- Class 2 (6,000–10,000 lbs): $190 for full EVs, $100 for plug-in hybrids
- Class 3 (10,001–26,000 lbs): $340 for full EVs, $210 for plug-in hybrids
- Class 4 (over 26,001 lbs): $1,100 for full EVs, $700 for plug-in hybrids
The revenue goes into the same highway restricted account that receives most gasoline and diesel tax dollars.8Alternative Fuels Data Center. Electricity Laws and Incentives in Montana Starting July 1, 2028, EV registration fees for private residents drop 30 percent. For a typical Class 1 passenger EV, that brings the annual fee to $91.