Seattle has no city gas tax. Every cent of fuel tax you pay at a Seattle pump comes from two fixed layers: 55.4 cents per gallon in Washington state excise tax and 18.4 cents per gallon in federal excise tax, for a combined 73.8 cents per gallon.1Washington Department of Revenue. Motor Vehicle Fuel Tax Rates On top of that, Washington’s cap-and-invest carbon program adds a variable cost that typically runs an estimated 25 to 50 cents per gallon, pushing the realistic all-in tax-and-carbon load above a dollar per gallon in 2026.
What You Pay Per Gallon Right Now
For the period from July 1, 2025, through June 30, 2026, every gallon of gasoline sold in Seattle carries at least 73.8 cents in fixed government taxes.1Washington Department of Revenue. Motor Vehicle Fuel Tax Rates The split:
- Washington state fuel tax: 55.4 cents per gallon.
- Federal excise tax: 18.3 cents for the Highway Trust Fund, plus 0.1 cent for the Leaking Underground Storage Tank fund, totaling 18.4 cents.
Neither rate moves with the price of crude. Whether the base price of gasoline is $2.50 or $5.00, the per-gallon tax is identical. The variable piece is the carbon allowance cost, which changes with Washington’s quarterly auction results.
The Washington State Portion
The 55.4-cent state tax is set by RCW 82.38.030, which imposes an excise tax on every gallon of motor vehicle fuel and diesel sold in Washington.2Washington State Legislature. RCW 82.38.030 Tax Imposed – Rate – Incidence – Allocation of Proceeds The current rate is up from 49.4 cents, where it had sat for several years. The 6-cent increase took effect in mid-2025 and puts Washington among the highest state fuel tax rates in the country.1Washington Department of Revenue. Motor Vehicle Fuel Tax Rates
Fuel distributors pay the tax before it reaches a station, at the point the fuel is removed from a terminal or refinery. The industry calls this collection “at the rack.”3Washington State Legislature. RCW Chapter 82.38 Fuel Tax Act By the time you swipe your card, the tax is already in the posted price. The station has no authority to adjust it.
Because the tax is a flat per-gallon amount and not a percentage of price, your total contribution scales with how much fuel you buy, not with what fuel costs.
The Federal Portion
Underneath the state tax, the federal government imposes 18.3 cents per gallon on gasoline plus a 0.1-cent surcharge for cleanup of leaking underground storage tanks.4Office of the Law Revision Counsel. 26 USC 4081 Imposition of Tax Diesel carries a higher federal rate of 24.4 cents per gallon. These rates have been frozen since 1993 and are not indexed to inflation.
The Carbon Cost on Top
Washington’s Climate Commitment Act, codified as RCW Chapter 70A.65, created a cap-and-invest program that acts as a separate cost layer on fuel.5Washington State Legislature. RCW Chapter 70A.65 Greenhouse Gas Emissions – Cap and Invest Program Fuel suppliers that produce or import enough fossil fuel to generate 25,000 or more metric tons of carbon dioxide annually must buy emission allowances from the state. The Department of Ecology runs at least four auctions a year, and suppliers treat the allowance cost as a business expense passed through to drivers.
Prices have swung since the program launched in 2023. Early auctions settled in the high $40s and $50s per metric ton, climbed above $60, and reached $70.86 per metric ton for current-vintage allowances in December 2024. A March 2025 auction settled at $50. Translating those numbers into cents per gallon is imprecise because it depends on the carbon intensity of the fuel blend, but state agency and independent estimates put the pump impact roughly in the range of 25 to 50 cents per gallon.
Voters had a chance to kill the program in November 2024 through Initiative 2117, which proposed repealing the Climate Commitment Act. It failed, with about 62 percent voting to keep the program.
Legally, the carbon cost is not a “tax.” It is the price of an allowance, and that distinction matters for where the money goes.
Where the Money Goes
The Washington Constitution contains one of the strictest fuel-tax spending restrictions in the country. Article II, Section 40, adopted in 1944, requires every dollar collected from motor vehicle fuel taxes to go into a special fund used exclusively for highway purposes.6Office of the Attorney General. Applicability of Article II Section 40 of the Washington Constitution to Proposed Excise Tax The legislature cannot move this money to schools, healthcare, or general operations.
“Highway purposes” is defined broadly: road construction and maintenance, bridge repairs, traffic signals, state patrol operations, and the ferry system. In Seattle, those dollars show up as pavement overlays, bridge work, and operational funding for Washington State Ferries. The constitutional language also reaches county roads and city streets, so a share flows to local governments.
Federal fuel tax dollars go into the Highway Trust Fund, which splits spending between highway infrastructure and mass transit capital projects. Unlike the state fund, it has no constitutional protection.
Carbon auction revenue is a separate stream. It funds transit expansion, electric vehicle infrastructure, wildfire resilience, and other climate programs, and it is not locked to highway spending.
Refunds If You Don’t Drive on Public Roads
If you burn fuel for something other than driving on public roads, you can recover the state fuel tax you paid. RCW 82.38.180 allows refunds for fuel used in boats, construction equipment, farm machinery, and other off-road applications.7Washington State Legislature. RCW 82.38.180 Refund of Tax The logic: the tax maintains roads, so fuel that never touches a road should not carry it.
Your claim has to be worth at least $20, which at 55.4 cents per gallon works out to roughly 36 gallons. You have 13 months from the date of purchase to file, and you will need the original invoices showing tax paid.7Washington State Legislature. RCW 82.38.180 Refund of Tax Keep every receipt from the start; most denied claims fall apart on documentation.
Claims go through the Washington Department of Licensing’s License Express portal, which replaced the older Taxpayer Access Point system in March 2025.8Washington State Department of Licensing. License Express for Prorate and Fuel Tax Paper claims by mail are still accepted. On the federal side, Form 4136 lets you claim a credit for federal fuel tax paid on off-highway uses when you file your income tax return.9Internal Revenue Service. About Form 4136 Credit for Federal Tax Paid on Fuels
One warning on the diesel side. Diesel sold for off-road use is dyed red to signal that highway fuel taxes were never paid on it. Running dyed diesel in a vehicle driven on public roads is illegal under both federal and state law, and inspectors can test the fuel in your tank during roadside stops. The federal penalty under 26 USC 6715 is $1,000 or $10 per gallon of dyed fuel in the tank, whichever is greater, and that base multiplies for repeat offenders.10GovInfo. 26 USC 6715 Dyed Fuel Sold for Use or Used in Taxable Use Both the driver and the business owner can be held liable.
What EV Drivers Pay Instead
Electric vehicle owners pay no fuel tax, but Washington recovers some of that lost revenue through an annual registration surcharge. Under RCW 46.17.323, battery electric vehicles pay an additional $150 per year at renewal: a $100 base fee plus a $50 supplemental fee.11Washington State Legislature. RCW 46.17.323 Electric Vehicle Registration Renewal Fees The vehicle must be capable of traveling at least 30 miles on battery power alone to trigger the fee.