For the period running July 1, 2025 through June 30, 2026, the Washington state gas tax is 55.4 cents per gallon on gasoline and 58.4 cents per gallon on diesel.1Washington Department of Revenue. Motor Vehicle Fuel Tax Rates Add the 18.4-cent federal excise tax on gasoline (24.4 cents on diesel), and every gallon carries roughly 73.8 cents in direct fuel taxes before you factor in Washington’s carbon program, which adds a separate, variable cost that can push the total government-imposed charge past $1.30 per gallon in some periods.
What You Pay Per Gallon Right Now
The statutory base rate set by RCW 82.38.030 is 49.4 cents per gallon.2Washington State Legislature. RCW 82.38.030 – Tax Imposed Additional levies enacted through transportation funding packages bring the effective rate to the current 55.4 cents on gasoline and 58.4 cents on diesel. These are fixed amounts per gallon, not percentages, so the tax stays flat whether pump prices rise or fall.
Federal excise tax stacks on top. Gasoline carries 18.4 cents per gallon (18.3 cents in excise plus a 0.1-cent Leaking Underground Storage Tank fee), and diesel carries 24.4 cents (24.3 cents plus the same 0.1-cent fee).3U.S. Energy Information Administration. How Much Tax Do We Pay on a Gallon of Gasoline and on a Gallon of Diesel Fuel Combined, a Washington driver pays about 73.8 cents in fuel taxes on every gallon of regular gasoline and roughly 82.8 cents on every gallon of diesel.
You never see any of this as a line item. Fuel distributors collect the state tax and remit it to the Washington Department of Revenue, and the federal portion is collected at the terminal rack before fuel reaches the station. It is all built into the posted pump price.
The Carbon Cost That Isn’t Called a Tax
The biggest variable in what you actually pay at the pump comes from the Climate Commitment Act, codified in chapter 70A.65 RCW. The law requires fuel suppliers and other large emitters to buy carbon allowances for every metric ton of greenhouse gas they produce, and suppliers pass that cost through to consumers.4Washington State Legislature. Chapter 70A.65 RCW – Greenhouse Gas Emissions – Cap and Invest Program
The Department of Ecology runs quarterly auctions of a limited supply of allowances.5Washington State Department of Ecology. Auctions and Market Because prices are set by bidding, the per-gallon impact moves with each cycle. Settlement prices since the program launched have ranged from roughly $30 to over $70 per metric ton of CO2, translating to an estimated 25 to 60-plus cents per gallon. The December 2025 auction settled at $70.86 per metric ton for current-vintage allowances.
The CCA cost is legally treated as a regulatory compliance expense, not a tax. That classification matters because the revenue is not restricted to highway spending. CCA proceeds fund public transit, clean energy projects, air quality improvements in overburdened communities, and other climate initiatives. Quarterly auctions are continuing on schedule in 2026.
Where Washington’s Gas Tax Money Has to Go
Article II, Section 40 of the Washington Constitution, known as the 18th Amendment, requires every dollar of state motor vehicle fuel tax to go into a dedicated 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 that money to schools, social services, or the general fund.
Qualifying highway purposes include:
- Building, repairing, and maintaining state highways, county roads, bridges, and city streets, and buying rights-of-way
- Installing and operating traffic signs and signals
- Funding Washington State Patrol policing of public highways
- Operating movable-span bridges and state ferries that form part of the highway system
- The engineering, legal, and administrative costs of running the highway system and collecting the tax itself
Anything outside that list, including public transit and bike infrastructure, has to be funded from other sources. The CCA is one of those sources, which is part of why the two revenue streams are kept legally distinct.
Refunds When You Pay Tax on Fuel You Didn’t Drive On
If you paid Washington fuel tax on gasoline or diesel that never propelled a vehicle on a public road, you can claim it back. Common qualifying uses include farm equipment, generators, and boats.7Washington State Legislature. Chapter 82.38 RCW – Motor Vehicle Fuel Tax Refunds are also available for fuel exported out of state, fuel destroyed by fire or flood, and fuel consumed by separately metered power take-off equipment on a vehicle.
Diesel has extra categories: fuel used by special mobile equipment such as construction cranes or well-drilling rigs, fuel used moving between two pieces of private property where road travel is incidental, and diesel accidentally mixed with dyed (untaxed) fuel. Private nonprofit transportation providers serving people with special transportation needs can also claim gasoline refunds.
The federal portion is handled separately. The IRS offers a refundable credit of 18.3 cents per gallon of gasoline and 24.3 cents per gallon of undyed diesel used for off-highway business purposes or on a farm for farming purposes. You claim it on IRS Form 4136 with your federal return.8Internal Revenue Service. About Form 4136, Credit for Federal Tax Paid on Fuels Dyed diesel is already exempt from federal excise tax at purchase and does not qualify.
What EV and Hybrid Drivers Pay Instead
Drivers who buy little or no gasoline still use the roads, and Washington captures that through annual registration surcharges. A fully electric vehicle pays two fees at each renewal: a $150 EV registration renewal fee under RCW 46.17.323,9Washington State Legislature. RCW 46.17.323 – Electric Vehicle Registration Renewal Fees and a $75 transportation electrification fee under RCW 46.17.324.10Washington State Legislature. RCW 46.17.324 – Transportation Electrification Fees Together that is $225 a year on top of standard registration costs, collected by the Department of Licensing, county auditors, and their appointed agents at tab renewal.
Hybrids that cannot travel at least 30 miles on battery power alone skip the $150 EV fee but still pay the $75 electrification fee. Both fees apply only to vehicles designed to exceed 35 miles per hour, so low-speed neighborhood electric vehicles and golf carts are excluded.
Interstate Truckers and IFTA
If you run a qualified commercial vehicle across state lines, your fuel tax obligations run through the International Fuel Tax Agreement rather than pump-level collection alone. IFTA lets a carrier register in one base jurisdiction and file a single quarterly return that allocates fuel tax to each state based on miles driven there. Washington participates, and the Department of Licensing handles licensing and returns for carriers based here.11Washington State Department of Licensing. Filing IFTA Tax Returns
Returns are due every quarter even if you had no mileage or stayed inside Washington. Late filing brings a penalty of $50 or 10 percent of tax due, whichever is greater, plus monthly interest. Not filing at all can cost you your license.