How California's smog check works

California's smog check is a vehicle emissions test required every two years for most cars, or annually for vehicles over 8 years old in certain counties. The test measures whether your vehicle's exhaust meets state pollution standards. A licensed smog check station reads your vehicle's onboard diagnostic system and may perform a tailpipe test, depending on your vehicle's age and type.

The state maintains a database of all smog check results. When you pass, the station reports it electronically to the Department of Motor Vehicles (DMV). You do not receive a paper certificate — the DMV has the record. If you fail, you get a written report showing which emissions systems did not meet standards, and you have 30 days to repair and retest at no additional fee.

Key Takeaways

  • California requires a smog check every two years for most vehicles, or every year if your car is over 8 years old in certain counties.
  • A passing smog check is reported directly to the DMV by the testing station, so you do not need to bring paperwork to your registration renewal.
  • If you fail, you have 30 days to make repairs and retest for free at the same station.
  • Vehicles registered outside California, newly purchased vehicles, and certain electric or hybrid models may be exempt from smog check requirements.

When your smog check is due

Your smog check due date is tied to your vehicle registration expiration date. The DMV will not renew your registration without a passing smog check result on file. You can take the test up to 90 days before your registration expires, so plan accordingly if you know your vehicle may need repairs.

If your registration has already expired, you can still get a smog check and renew, but you may face late fees. Some counties have different timing rules — for example, San Francisco and Alameda County require annual testing for vehicles over 8 years old instead of the standard two-year cycle. Check your county's specific requirements on the Bureau of Automotive Repair website or ask your local smog station.

Where to get a smog check and what it costs

You must use a station licensed by the Bureau of Automotive Repair (BAR). The state does not set a fixed price, so costs vary by location and station. Most smog checks range from $30 to $80 for a basic test. You can search for licensed stations on the BAR website by entering your zip code.

Some stations charge extra for specific services — for example, if your vehicle requires a more complex test (such as a two-speed idle test for older cars) or if you need a retest after repairs. Ask the station for the full price before you start the test. If a station seems unusually expensive, call another location in your area to compare.

What happens if you fail the smog check

A failed smog check means one or more of your vehicle's emissions systems did not meet state standards. The station will give you a written report listing the specific systems that failed — typically the catalytic converter, oxygen sensors, fuel system, or engine controls. This report tells a mechanic what to repair.

You have 30 days from the test date to make repairs and return to the same station for a free retest. If you retest at a different station, you will pay the full test fee again. Keep your original failing test report; you will need it to show the retest station. If repairs cost more than you expected, some nonprofits and local programs offer low-income vehicle repair information, though availability varies by county.

Vehicles exempt from smog check

Not all vehicles require a smog check. Vehicles registered outside California are exempt while they remain out-of-state. New vehicles (current model year) are exempt for their first registration. Most electric vehicles and plug-in hybrids are exempt. Vehicles over 40 years old registered as classic or collector vehicles are also exempt, though they must meet specific registration requirements.

Vehicles with a salvage or non-repairable title cannot pass a smog check and cannot be registered for road use. If you are unsure whether your vehicle is exempt, the DMV website has a full list by vehicle type and year, or you can call your local DMV office.

What to do if your vehicle fails repeatedly

If your vehicle fails a second time after repairs, you may be may be able to access for the Smog Check Referee Program. This program allows you to take your vehicle to a state-operated referee station for a second opinion on the test results. Referee stations charge a fee (typically $70 to $100) and can override a failed test if they determine the station's equipment was faulty or the test was performed incorrectly.

If your vehicle fails a third time, you may be may be able to access for the Consumer information Program (CAP), which can help pay for repairs or, in some cases, help you retire the vehicle and purchase a cleaner replacement. CAP has income limits and other requirements. Contact your county's air quality management district or the Bureau of Automotive Repair to learn whether your situation qualifies.

Frequently Asked Questions

Can I renew my registration without a smog check?

No. The DMV will not process a registration renewal without a passing smog check result on file. You must complete the test before your current registration expires. If your registration has already expired, you can still get a smog check and renew, but you may owe late fees.

What if I just bought a used car and it fails smog check?

If you bought the car recently, you may have a brief window to return it or negotiate repairs with the seller, depending on your purchase agreement. Once you own it, you are responsible for repairs. If the cost is high, ask the smog station whether your vehicle might may have access to for repair information programs in your county.

Do I need to bring my smog check paperwork to the DMV?

No. The smog station reports the result electronically to the DMV. You do not need to bring anything to your registration renewal appointment. The DMV will see the passing result in their system.

What if I move out of California after my smog check?

Your California smog check is only valid in California. If you move to another state, you will follow that state's emissions testing rules. If you move back to California later, you will need a new smog check based on your new registration date.

Can I get a smog check before my registration expires?

Yes. You can take the smog check up to 90 days before your registration expires. This gives you time to make repairs if needed and still renew on time. The test result is valid for the full two-year registration period once you pass.