IFTA Tax Rates in Colorado (2026)
Colorado taxes diesel at 33.5 cents per gallon and gasoline at 28.0 cents under IFTA. Here is what sits inside those rates, how they hit your quarterly return, and the fueling plays on I-70, I-25 and I-76 where four cheaper states are a tank away.
By the HaulMath editorial team · Updated $1
Key numbers at a glance
| Fuel type | Rate | Notes |
|---|---|---|
| Diesel (special fuel) | 33.5¢/gal ($0.335) | Effective with the July 2026 adjustment; the figure for your return's diesel line |
| Gasoline | 28.0¢/gal ($0.280) | Also set with the July 2026 adjustment; up from 27.0 cents in Q1 2026 |
| Gasohol / ethanol blends | 28.0¢/gal ($0.280) | Reported with gasoline at the same rate |
| Biodiesel / B-blends | 33.5¢/gal ($0.335) | Reported as diesel on the Colorado line |
Colorado is the high-altitude crossroads of the interior West — I-70 over the Rockies, I-25 from Wyoming to New Mexico, I-76 out toward Nebraska. Its fuel taxes combine base excise with environmental and infrastructure fees, and the totals reset each July 1, which matters when your Q2 and Q3 returns use different numbers. The figures below are from the official IFTA Inc. fourth quarter 2026 tax rate matrix and Colorado Department of Revenue IFTA publications — as of Q4 2026 — always confirm the current quarter's official IFTA matrix before filing (this quarter's matrix is not final until December 4, 2026). Compare every jurisdiction on the IFTA rates by state hub.
IFTA tax rates in Colorado
Colorado's published IFTA rates combine the state excise tax with several statutory fees; the Colorado DOR IFTA rate tables republish them each quarter:
| Fuel type | Rate | Notes |
|---|---|---|
| Diesel (special fuel) | 33.5¢/gal ($0.335) | Effective with the July 2026 adjustment; the figure for your return's diesel line |
| Gasoline | 28.0¢/gal ($0.280) | Also set with the July 2026 adjustment; up from 27.0 cents in Q1 2026 |
| Gasohol / ethanol blends | 28.0¢/gal ($0.280) | Reported with gasoline at the same rate |
| Biodiesel / B-blends | 33.5¢/gal ($0.335) | Reported as diesel on the Colorado line |
| E-85 | 28.0¢/gal ($0.280) | Taxed at the gasoline rate |
Colorado's diesel running about 5.5 cents above its gasoline is the structure to watch: excise plus fee components stack differently for special fuels. The combined rate also explains why third-party comparisons quote slightly different totals — the Tax Foundation's July 2026 figures of 30.18 cents gasoline and 35.68 cents diesel include additional fee layers beyond the IFTA-reportable rate. File the IFTA matrix number, not the think-tank number. There is no separate Colorado surcharge line; Indiana-style surcharge schedules and Virginia's two-line split do not apply here.
How Colorado IFTA affects your filings
Your Colorado line each quarter is Colorado miles divided by fleet MPG, times $0.335 for diesel. Take a Denver hub run stretching into Nebraska and Wyoming at 6.5 MPG:
| State | Miles | Gallons at 6.5 MPG | Diesel rate | Tax owed |
|---|---|---|---|---|
| Colorado | 220 | 33.8 | $0.335 | $11.34 |
| Nebraska | 180 | 27.7 | $0.318 | $8.81 |
| Wyoming | 150 | 23.1 | $0.240 | $5.54 |
| Total | 550 | 84.6 | — | $25.69 |
Colorado is 40% of the miles and 44% of the tax — middle of the regional pack, cheaper than Utah, dearer than everything else on the map's edges. Flip the fueling: buy all 84.6 gallons in Colorado and you prepaid $28.35 against $25.69 owed, roughly a wash. Buy them in Wyoming and you prepaid $20.31 against $25.69, leaving $5.38 due. The mountain wrinkle is MPG: grades over the Eisenhower Tunnel or Vail Pass can pull a 6.5-MPG truck toward 5.8 on loaded westbounds, and since IFTA uses one fleet-average MPG, every tenth you shave off the real average silently shifts tax between states. Run your actual numbers in the IFTA calculator, recompute MPG every quarter, and file each quarter with that quarter's matrix — the July 1 change means Q2 and Q3 returns rarely match.
Fueling strategy around Colorado: price minus tax
Shop by net price: pump price minus the state tax, then check the rates ahead. The Q4 2026 neighbor map — Wyoming 24.0 cents, Nebraska 31.8, Kansas 26.0, Oklahoma 19.0, New Mexico 21.0, Utah 37.9 — makes Colorado a fill-up state only when you are heading west into Utah, where filling in Denver or Grand Junction first saves 4.4 cents a gallon. Southbound on I-25, New Mexico's 21.0 cents is 12.5 cents cheaper: hold range to Raton or fill in New Mexico outright. Eastbound on I-76 and I-70, Nebraska and Kansas both undercut Colorado, so top off at the border rather than deep inside the state. A hundred gallons a week moved from Colorado pumps to Wyoming or New Mexico pumps is roughly $500 to $650 a year in tax timing. Weekly diesel swings can dwarf those gaps, so anchor the decision to your rates with the fuel surcharge guide — surcharge recovers the benchmark; fueling strategy keeps the IFTA line quiet.
FAQ
What is the current IFTA fuel tax rate in Colorado?
As of Q4 2026, Colorado's IFTA rate is 33.5 cents per gallon on diesel and 28.0 cents per gallon on gasoline, per the official IFTA Inc. tax rate matrix. Colorado reviews rates effective July 1 each year — always confirm the current quarter's official IFTA matrix before filing.
How often do Colorado fuel tax rates change?
Colorado adjusts its fuel tax rates each July 1, when the excise and fee components are reviewed. The Q4 2026 figures — 33.5 cents diesel, 28.0 cents gasoline — reflect the July 2026 adjustment, so Q1 2027 filings should pull a fresh matrix.
Does Colorado have an IFTA surcharge tax like Indiana or Virginia?
No separate surcharge schedule. Colorado files one combined rate per fuel type on the IFTA return; the environmental and infrastructure fees are already inside the 33.5-cent diesel figure. The two-line surcharge structure used by Indiana and Virginia does not apply.
How do I calculate the fuel tax owed for miles driven in Colorado?
Taxable gallons = Colorado miles divided by your truck's MPG. Tax owed = taxable gallons times $0.335 (diesel, Q4 2026). At 6.5 MPG, 220 Colorado miles burn 33.8 gallons and owe about $11.34 to Colorado on your IFTA return.
Where should I buy fuel around Colorado to lower my IFTA bill?
Colorado diesel at 33.5 cents beats Utah's 37.9 cents but loses to New Mexico (21.0), Oklahoma (19.0), Wyoming (24.0), Kansas (26.0) and Nebraska (31.8). On I-70 westbound, fill in Colorado before Utah; on I-25 south or I-76 east, top off in New Mexico, Wyoming or Nebraska first.
Do mountain grades change my Colorado IFTA math?
Yes, through MPG. IFTA uses one fleet average MPG, and climbing the Eisenhower Tunnel grades or Wolf Creek Pass drags it down, which raises taxable gallons in every state on the return. Recalculate your quarterly MPG honestly — inflated MPG understates Colorado tax and is a common audit finding.