California Per-Mile Tax: Rate, Tracking, and Privacy Rules

California’s per-mile tax, officially called the Road Charge, is a proposed mileage-based fee the state has been testing as a possible replacement for its gasoline excise tax. Nothing is mandatory today. Every phase so far has been voluntary, the most recent collection pilot wrapped up in January 2025, and a final report to the Legislature is due by December 31, 2026.¹ The authorizing law sunsets on January 1, 2027, so unless the Legislature acts, the research program simply ends.²

Why the State Is Studying a Mileage Fee

California’s gas tax, currently 61.2 cents per gallon as of July 2025, brings in less money every year.³ Cars are more fuel-efficient. More drivers have switched to electric vehicles that never buy gasoline. An EV puts the same wear on the pavement as a gas sedan but contributes nothing at the pump.

The state partially addresses this today by charging owners of model year 2020 and later zero-emission vehicles a $121 annual Road Improvement Fee at registration.⁴ But a flat fee treats a 5,000-mile-a-year driver the same as a 25,000-mile-a-year driver. A per-mile charge would tie each driver’s contribution to actual road use regardless of what powers the vehicle.

Where the Program Stands Right Now

The most recent phase, the Road Charge Collection Pilot, ran from August 2024 through January 2025. Volunteers drove normally, paid a real monthly road charge based on miles driven, and received credits at the end to offset the gas taxes and EV fees they had already paid during the study.¹

That pilot has concluded. The state is now analyzing results for its final legislative report. No California driver is required to pay a per-mile charge, and the rates used in the pilots are hypothetical figures set for research purposes. Any permanent rate would need to be set by the Legislature.⁵

What a Per-Mile Charge Would Cost

The official Road Charge site has modeled hypothetical rates of two, three, and four cents per mile.⁵ California drivers average roughly 14,000 to 15,000 miles a year. At those rates, the annual charge would run about:

Two cents per mile: $280 to $300 per year
Three cents per mile: $420 to $450 per year
Four cents per mile: $560 to $600 per year

For comparison, a driver who gets 25 miles per gallon and drives 14,500 miles pays about $355 a year in state gas tax at the current 61.2-cent rate. Under the vehicle-specific rate the pilot tested, that same driver would land near 2.4 cents per mile, close to what they already pay. The real shift falls on fuel-efficient hybrids and EVs, which would likely pay more under a per-mile system, and on less efficient trucks and SUVs, which could pay about the same or slightly less because their fuel bills already carry a high per-mile tax load.

How the Rate Would Be Calculated

Senate Bill 339, signed in 2021, required the collection pilot to split participants into two billing groups:²

A flat-rate group, where every driver paid the same per-mile fee set by the Technical Advisory Committee.
A vehicle-specific group, where each driver’s rate was calculated by dividing the state gas tax by the EPA’s estimated fuel economy for that make, model, and year.

The vehicle-specific math is the key to understanding how the program is designed to feel fair. A 30 mpg car pays roughly two cents per mile in gas tax at the current rate. A 15 mpg truck pays about four cents. Mirroring that in a mileage charge keeps gas-powered drivers roughly where they are today, while bringing EVs and hybrids into the system based on actual road use.

How Mileage Would Be Tracked

Participants chose from several reporting methods, and the choice matters because it decides what data is collected.

Manual odometer reporting. You photograph your odometer on a schedule and upload the images. No hardware, no GPS, no location data. Works on any vehicle, including older ones.
OBD-II plug-in device. A small device plugs into the diagnostic port found in most vehicles built after 1996 and reports mileage automatically. Some versions include GPS to separate in-state from out-of-state miles; simpler versions only record distance.
Built-in vehicle telematics. Newer cars with factory connectivity can send mileage directly, no extra hardware needed.
Smartphone app. Uses the phone’s sensors to track distance, with or without location data depending on the configuration.

If you don’t want location data collected, the manual odometer option exists specifically for that reason. The program was built so no one is forced into a tracking method they’re uncomfortable with.

Will Drivers Pay Twice?

No, and this is the question most people raise first. During the collection pilot, participants with gas vehicles paid their monthly road charge and then received a credit at the end for the state fuel taxes paid at the pump during the study.¹ SB 339 specifically requires that participants “receive a credit or a refund for the estimated state fuel taxes and electric vehicle fees paid to operate a vehicle during the pilot.”²

EV owners don’t pay gas tax, so their offset came as a prorated credit of the $121 annual Road Improvement Fee.¹ A permanent system would be designed to replace both the gas tax and the EV registration fee with a single per-mile charge, so drivers see one road-funding cost rather than several layered ones.

What About Out-of-State Miles?

Driving to Nevada or Oregon shouldn’t trigger a California charge, and the state has studied how to make sure it doesn’t. GPS-enabled tracking methods can separate in-state from out-of-state miles automatically. For the manual odometer method, which only records total distance, the pilots examined self-reported trip logs and reconciliation approaches. Building a reliable solution at scale is one of the design challenges the research is meant to resolve.

Privacy Rules Governing the Program

The California Transportation Commission adopted twelve privacy principles that have guided every pilot phase. The ones that matter most to a prospective participant:

No location tracking required. A non-GPS option must always be available.
Data minimization. Only information needed to calculate and collect the charge can be gathered.
No secondary use. Personal data cannot be shared outside the program without the driver’s consent, specific legal authority, or a court order.
Driver access. Participants can see what’s stored and request corrections.
Data destruction. Information kept beyond what’s needed for payment must be stripped of personal details and used only for public purposes like safety research.⁶

What Happens Next

The final report on the collection pilot is due to the Legislature by December 31, 2026, and the authorizing statute sunsets on January 1, 2027.² From there, legislators will decide whether to extend research, build toward a mandatory statewide system, or move on. Whether any additional volunteer opportunities open before the sunset depends on decisions that haven’t been announced. If the Legislature does nothing, no per-mile charge takes effect.

1
California Road Charge. Road Charge Collection Pilot
2
LegiScan. Bill Text: CA SB339 – Chaptered
3
California Department of Tax and Fee Administration. Fuel Taxes
4
California DMV. Registration Fees
5
California Road Charge. California Road Charge
6
California Transportation Commission. Road Charge Technical Advisory Committee Memorandum