IFTA explained: who needs it, the quarterly deadlines and how the return works

IFTA, the International Fuel Tax Agreement, lets a carrier running qualified vehicles in two or more states or provinces file one fuel tax return each quarter with its home (base) jurisdiction instead of dealing with every state separately. The base jurisdiction then shares the tax out according to where the fuel was actually burned. Returns are due April 30, July 31, October 31 and January 31, and must be filed even for a quarter with no activity.

IFTA is administered by the member jurisdictions under the IFTA Articles of Agreement. The IFTA organization’s own site blocks automated access from our research machine, so the rules on this page are taken from base jurisdictions’ official pages, mainly the Colorado Department of Revenue, which quotes the Articles of Agreement by rule number, and the Alabama Department of Revenue. Where something is a Colorado practice rather than an IFTA-wide rule, we say so.

What IFTA does

Every state taxes the diesel or gasoline burned on its roads, but a truck can cross a state without buying fuel there. IFTA fixes that. In Colorado’s words, IFTA "is not an additional tax. It redistributes the tax to the state where the fuel was actually used versus where it was purchased." Colorado describes the membership as all 48 contiguous states and 10 Canadian provinces, each a "member jurisdiction," with your "base jurisdiction" being the one that issues your credentials.

Who needs an IFTA license

You need IFTA credentials (or a fuel trip permit for each trip, see below) if you operate a qualified motor vehicle in two or more member jurisdictions. Article II, R245 of the Articles of Agreement, as quoted by Colorado, defines it as a motor vehicle used, designed or maintained for transportation of persons or property and:

• .100 having two axles and a gross vehicle weight or registered gross vehicle weight exceeding 26,000 pounds (11,797 kg); or
• .200 having three or more axles, regardless of weight; or
• .300 used in combination, when the weight of the combination exceeds 26,000 pounds (11,797 kg) gross vehicle or registered gross vehicle weight.

Recreational vehicles are excluded (R248): motor homes, pickups with campers and buses "used exclusively for personal pleasure," and "the vehicle cannot be used in connection with any business endeavor."

Carriers that stay inside one state do not need IFTA. Colorado puts it plainly: "Motor carriers that are based in Colorado but do not travel out of state do not qualify for IFTA." Their fuel tax is paid at the pump under state law. For the wider question of which rules apply to in-state work, see interstate vs intrastate.

Base jurisdiction, license and decals

Your base jurisdiction is where your qualified vehicles are based for registration and where some of the fleet’s travel happens (R212, as quoted by Colorado). You get one license from it for the whole fleet. In Colorado, for example:

• The applicant needs a valid business registration, a vehicle registered in Colorado (IRP or county, not a temporary registration), and no unpaid IFTA taxes or returns anywhere; the name and federal tax ID must match the vehicle registration.
• The license is valid for the calendar year and expires December 31. A copy must be carried in each qualified vehicle: "A vehicle will not be considered operating under IFTA unless there is a copy of the license in the vehicle."
• Decals are issued per calendar year for each qualified vehicle. Colorado’s instruction: "attach one decal to each side of the vehicle’s cab, in the lower rear corner." Colorado charges no fee for the license or decals; other jurisdictions set their own.
• Renewal: during January and February each year, "a valid IFTA license and decals from the previous year will be honored by IFTA member jurisdictions," so current credentials must be in place by March 1.
• Since 1 January 2019 carriers can carry the IFTA license as an electronic image, according to the DC DMV’s IRP page.

Missing decals or no license copy can mean a citation and having to buy a trip permit on the spot. Colorado sells trip permits at its ports of entry; weigh stations and ports are where credentials are usually checked (see our weigh station directory).

The quarterly due dates

These are the dates published by both Colorado and Alabama. When a due date falls on a Saturday, Sunday or legal holiday, Colorado treats the next business day as the due date. Returns can be filed from the first day after the quarter ends (Alabama). For 2026 that means the Q3 return is due October 31, 2026, which is a Saturday, so under Colorado’s rule it is due Monday, November 2; confirm with your own base jurisdiction.

File even with nothing to report. Colorado requires a return each quarter "whether they have activity to report or not." One return covers the whole IFTA fleet.

How the return is calculated

You report four sets of numbers for all qualified vehicles in the fleet (Colorado’s filing instructions):

• Total miles in all jurisdictions, rounded to the nearest mile;
• Total gallons of fuel purchased and placed in the propulsion tanks;
• Miles by jurisdiction;
• Tax-paid gallons by jurisdiction, the fuel you bought in each one.

From these, the return works out:

1. Fleet average MPG = total miles / total gallons.
2. Taxable gallons in each jurisdiction = taxable miles there / fleet MPG. Colorado: taxable gallons "are the gallons used while traveling through each jurisdiction."
3. Net taxable gallons = taxable gallons minus tax-paid gallons bought there.
4. Tax due or credit = net taxable gallons x that jurisdiction’s rate for the quarter. Positive results are tax owed; negative results are credits.

Each jurisdiction’s rate can change every quarter; the rates are published in IFTA’s quarterly tax rate table, and base jurisdictions post them with their forms (Colorado’s page is titled "Forms & Rate Tables"). Report every fuel purchase you have receipts for: as Colorado’s FAQ puts it, reporting all purchases as tax-paid gallons "will reduce the amount owed."

Worked example

Example with made-up tax rates, for illustration only. These are not any state’s actual rates. One truck runs 30,000 miles in a quarter and buys 5,000 gallons, so fleet MPG is 6.0.

The truck burned fuel in State C that it bought in A and B. State C is owed tax for it; A and B credit back tax collected at their pumps. The net goes to or from the base jurisdiction, which settles with the others. Fuel cost per mile, one of the biggest numbers in trucking, can be modelled in the cost per mile calculator.

What does not go on the return

• DEF is not fuel and is left out of total gallons (Colorado).
• Reefer fuel used in refrigeration units is excluded (Colorado).
• Miles run under a fuel trip permit are included in total miles but can be deducted from taxable miles, with a copy of the permit (Colorado).
• Toll roads and separate state mileage or weight taxes are not IFTA; miles on them are generally not deductible (Colorado).

Records: keep them four years

Colorado: "All records used to support reported miles and fuel must be retained for a period of four years." Records must be produced on request, and if they are not, the department "will make a determination based upon the information available."

Distance records

Colorado accepts its Individual Vehicle Distance Record or trip reports (including from on-board devices) that show: trip start and end dates; origin and destination with city and state; route with beginning and ending odometer readings by jurisdiction; total trip miles; miles by jurisdiction; vehicle unit number; fleet number; and your name.

Fuel receipts

Each receipt must show the date, seller’s name and address, gallons or liters, fuel type, price per gallon or total sale, the unit number of the vehicle fueled, and the purchaser’s name. With fuel cards, the department must be able to tie each fueling to a specific qualified vehicle, and Colorado recommends vehicle-specific cards. Bulk fuel withdrawals from your own tank need their own log (date, gallons, fuel type, unit number) plus invoices showing the tax was paid.

Penalties, interest and audits

• Late filing or payment: Colorado’s penalty is "the greater of $50 or 10% of the tax due." Interest runs at the IFTA annual interest rate, and "a full month’s interest is charged for any portion of a month." Interest is computed on the tax due to each member jurisdiction.
• Missing returns: Colorado bills estimated tax for the period and "may also revoke or suspend the license" of a licensee who does not file.
• Electronic filing: Colorado is phasing in mandatory electronic filing and payment by prior-year mileage (80,000 miles or more in 2025 from the filing period of March 31, 2026; 25,000 or more in 2026 from March 31, 2027; all licensees from March 31, 2028) and charges the greater of $50 or 5% of the tax due for not filing or paying electronically when required.
• Audits test the return against the distance and fuel records above. Thin records are the usual problem.

Trip permits instead of IFTA

If you qualify for IFTA but do not join, you must buy a fuel trip permit for each member jurisdiction you enter or pass through. Colorado’s example: a Colorado carrier without IFTA going into Wyoming "must purchase a Wyoming fuel trip permit." Each jurisdiction sets its own permit price. A trip permit is also the answer for a truck bought outside its base state on its way home to be registered.

IFTA vs IRP

Colorado’s FAQ: IRP "is an agreement to recognize the registration of commercial motor vehicles registered by other jurisdictions and provides for payment of apportioned licensing fees based on the total distance operated in all member jurisdictions. IFTA is an agreement to redistribute fuel tax based on where the fuel was used." The vehicle thresholds are the same, the same mileage records support both, and most carriers get both from the same base state. See IRP and apportioned plates, and how to get your own trucking authority for where IFTA fits in the start-up sequence.

Common mistakes

• Skipping a return for a quiet quarter. A zero return is still required.
• Losing fuel receipts. Unreported tax-paid gallons mean paying the tax twice.
• Estimating state miles instead of recording them trip by trip.
• Including DEF or reefer fuel in total gallons, which lowers your MPG and distorts every line.
• Running on last year’s decals after the end of February.