California’s smog law changes over the past two years touch nearly every vehicle owner in the state, though the effect depends on what you drive. Passenger car owners face a rolling eight-year smog check exemption paired with an annual abatement fee, tougher enforcement against aftermarket engine software, and, starting with the 2026 model year, a new wave of zero-emission requirements for new cars sold at California dealerships. Heavy-duty truck and bus owners have a separate compliance system, the Clean Truck Check program, with annual fees and mandatory emissions testing. Here’s how the current rules apply.
Smog Checks for Cars and Light Trucks
Gasoline-powered cars and light-duty trucks less than eight model years old don’t need a biennial smog inspection for registration renewal.1California Department of Motor Vehicles. Smog Inspections You pay an annual smog abatement fee instead: $20 for vehicles six model years old or newer, and $25 for model years seven and eight. Once your vehicle crosses that eight-year line, a smog check is required every two years at renewal.
Battery electric vehicles are fully exempt from smog inspections regardless of age.1California Department of Motor Vehicles. Smog Inspections Hybrids are not. A gas-electric hybrid gets the same rolling eight-year exemption as any gasoline car and then needs biennial checks after that.2Bureau of Automotive Repair. Smog Check: When You Need One and What’s Required
Diesel cars and trucks with a gross vehicle weight rating of 14,000 pounds or less need biennial smog checks, but 1997 and older diesels are exempt. Diesels over 14,000 pounds fall under the Clean Truck Check program instead.1California Department of Motor Vehicles. Smog Inspections
Your DMV renewal notice will tell you if the inspection has to happen at a STAR-certified station. STAR stations meet higher accuracy standards, and the requirement typically targets vehicles with a history of inspection issues or those flagged by the Bureau of Automotive Repair’s monitoring system.1California Department of Motor Vehicles. Smog Inspections
Smog Checks When Buying, Selling, or Moving In
The eight-year exemption is only for renewals. When a vehicle changes hands, a smog check is generally required before the sale, and the seller has to give the buyer a passing report.2Bureau of Automotive Repair. Smog Check: When You Need One and What’s Required Vehicles four model years old or newer skip the smog check for a change of ownership, but a smog transfer fee is still owed to the DMV. Transfers between immediate family members don’t require a smog check either.
Buying from a private seller? The vehicle must have passed within the last 90 days. From a dealership, the window is two years.
If you recently moved to California or bought a car out of state, plan for a smog check before you register. Vehicles coming into California for the first time need one for initial registration no matter what model-year exemption would otherwise apply.2Bureau of Automotive Repair. Smog Check: When You Need One and What’s Required
Software Modifications, Failed Tests, and Gross Polluter Fees
One area of tightened enforcement involves the Electronic Control Module. If a technician finds unauthorized software or aftermarket engine tunes that bypass factory emissions settings, the vehicle fails automatically. You have to restore it to original manufacturer specifications, or to a CARB-approved software version, before retesting.2Bureau of Automotive Repair. Smog Check: When You Need One and What’s Required This catches owners of modified trucks and performance cars off guard more than almost anything else in the process.
If your vehicle fails for other reasons, California’s repair cost waiver lets you obtain a passing certificate after spending at least $650 on qualifying emissions-related repairs at a licensed test-and-repair station. Diagnostics count toward the $650. The smog test itself does not. The waiver is limited to one per vehicle per registered owner and is only available for biennial renewal inspections. Change-of-ownership and initial California registration inspections don’t qualify.
Vehicles flagged as gross polluters face stiffer consequences. If you get a notice of noncompliance and don’t bring the vehicle to a test-only or licensed test-and-repair station within 30 days, an administrative fee of up to $500 gets tacked on at your next registration renewal or ownership transfer. Starting on the 31st day after the notice, the fee accrues at $5 per day up to the $500 cap.3California Legislative Information. California Health and Safety Code HSC 44081
Clean Truck Check for Heavy-Duty Vehicles
The Clean Truck Check program, created by Senate Bill 210 and also called the Heavy-Duty Inspection and Maintenance program, works like a smog check system for big rigs and buses.4California Air Resources Board. Facts About the Proposed Heavy-Duty Inspection and Maintenance Regulation It covers non-gasoline vehicles (diesel, natural gas, and other alternative fuels) with a gross vehicle weight rating over 14,000 pounds operating on California roads. Buses, motorhomes, and agricultural vehicles are all included.5California Air Resources Board. New California Requirements for On-Road and Off-Road Heavy-Duty Vehicles
Out-of-state trucks aren’t off the hook. If your rig is registered in Nevada or Arizona but operates in California, you still need a valid compliance certificate.4California Air Resources Board. Facts About the Proposed Heavy-Duty Inspection and Maintenance Regulation For California-registered vehicles, compliance is tied to DMV registration, so falling behind can block your renewal.
Registration, Fees, and Testing
Owners register through the Clean Truck Check portal at cleantruckcheck.arb.ca.gov.6California Air Resources Board. Clean Truck Check Vehicle Inspection System You’ll need the 17-digit VIN, the engine family name from the emission control information label under the hood, and contact information for the owner or fleet manager.
The annual compliance fee is $32.13 per vehicle as of January 1, 2026, adjusted from the original $30 base to match the California Consumer Price Index.7California Air Resources Board. Clean Truck Check Compliance Fee Update Effective 1/1/2026 Payment goes through the same portal.
Beyond registration and the fee, vehicles have to pass emissions compliance testing performed by a CARB-credentialed tester. That testing requirement took full effect on October 1, 2024, and every compliance deadline on or after January 1, 2025 requires a passing test. You can submit a passing test up to 90 days before your deadline to leave room for any repairs.8California Air Resources Board. Clean Truck Check – Overview Fact Sheet Some vehicles are subject to semi-annual testing depending on their engine model year and emissions profile.
When a Truck Gets Flagged
CARB uses a data-driven approach to flag potential high emitters. If your vehicle is flagged, you’ll receive a Notice to Submit to Testing and have 30 calendar days to submit a passing emissions test from a credentialed tester.8California Air Resources Board. Clean Truck Check – Overview Fact Sheet Vehicles that stay non-compliant face additional testing requirements, penalties, and potential registration holds. For California-plated trucks the registration hold is the real enforcement lever; for out-of-state trucks, the certificate itself gets checked during roadside inspections.
Cleaner New Trucks Under the Heavy-Duty Omnibus Rule
If you’re buying a new truck, the engine already meets tighter emission limits before it reaches the dealer. The Heavy-Duty Omnibus regulation took effect for 2024 model year engines and represents the most aggressive tightening of truck and bus emission limits in over a decade. For 2024 through 2026 model year engines, the nitrogen oxide standard drops 75 percent compared to the 2010 standard, and the particulate matter standard was cut in half. Even stricter standards apply to 2027 and later model years. The rule also extended warranty periods and useful-life requirements for emissions components, so manufacturers must stand behind their pollution controls for longer.9California Air Resources Board. Heavy-Duty Omnibus Regulation Fact Sheet
Advanced Clean Cars II and the 2026 Model Year
A separate regulation with major implications for new car buyers took effect with the 2026 model year. Advanced Clean Cars II, adopted by CARB in 2022, ramps up the percentage of new passenger vehicles that must meet zero-emission standards each year, reaching 100 percent by the 2035 model year. Battery electric vehicles and qualifying plug-in hybrids both count.10California Air Resources Board. Advanced Clean Cars II
The rule also introduces LEV IV, which tightens criteria pollutant standards on the conventional gas and hybrid vehicles still sold during the transition. For buyers, this means the new vehicles at California dealerships run cleaner than before, even if you’re not shopping for an EV. Over time, as more zero-emission vehicles hit the road, fewer cars will be subject to smog inspections at all.
Where the Federal Waiver Stands
California’s authority to set stricter vehicle emission rules than the federal government depends on a waiver under Section 209 of the Clean Air Act. The EPA must grant the waiver when California’s standards are at least as protective as federal ones, the state faces compelling and extraordinary conditions, and the rules are consistent with federal emissions law.11Office of the Law Revision Counsel. 42 U.S. Code 7543 – State Standards
The Heavy-Duty Omnibus regulation received its federal waiver in late 2024 or early 2025, and in December 2024 the U.S. Supreme Court declined to hear challenges to the constitutionality of the waiver program itself. The waiver’s long-term status remains a political question: the current federal administration has asked Congress to use the Congressional Review Act to reverse approval of both the Advanced Clean Trucks rule and the Omnibus regulation. For now, all of California’s major vehicle emission programs remain legally in effect.