How often you need a smog check in California

Most vehicles in California need a smog check every two years. If your vehicle is registered in California and is model year 1975 or newer, you will need one before you can renew your registration — but only every other year, not annually. The exact timing depends on when your vehicle was first registered in the state and what type of vehicle you own.

Vehicles model year 1975 and older, diesel vehicles, and some other categories are exempt from smog checks entirely. If you own a vehicle that falls into an exempt category, you will not need one at all, though you still need to register it with the California Department of Motor Vehicles (DMV).

Key Takeaways

  • Most California vehicles need a smog check every two years at renewal time, not every year.
  • Your smog check must happen within 30 days before your registration expires, or you cannot renew online or by mail.
  • Vehicles model year 1975 and older, most diesel vehicles, and motorcycles are exempt from smog checks.
  • If you buy a used vehicle in California, you may need a smog check before the sale can be completed, depending on the vehicle's age and type.
  • You can find a Bureau of Automotive Repair (BAR) certified smog station through the official California BAR website or by searching for "smog check" in your area.

The two-year smog check cycle and registration renewal

California's smog check requirement is tied to your vehicle registration renewal, not to a calendar date. When your registration is due to expire, you need a current smog check to renew it. A smog check is valid for 30 days before your registration expiration date and 30 days after — so you have a 60-day window to get one and still renew on time.

If you miss that window, you cannot renew your registration online or by mail. You will have to go to a DMV office in person and bring the smog check with you. After your registration expires, driving with an expired registration is illegal, even if you have a smog check certificate in hand.

The two-year cycle means that if your registration renews in March of this year, your next smog check is not due until March of the following year — and then not again until March two years after that. This is different from states that require annual inspections.

Which vehicles are exempt from smog checks

Not all registered vehicles need smog checks. Vehicles model year 1975 and older are permanently exempt. Most diesel vehicles are also exempt, though some newer diesel trucks and vans have different rules depending on their model year and weight. Motorcycles, motorized bicycles, and trailers do not need smog checks. Electric vehicles and plug-in hybrids are exempt as well.

Vehicles that are fewer than four model years old are exempt from their first smog check. For example, a vehicle registered in 2024 does not need a smog check until 2028. After that, the two-year cycle begins.

If you are unsure whether your vehicle is exempt, you can check the California DMV website or ask at a smog station. The station will tell you when ready whether your vehicle needs one.

Smog checks when you buy or transfer a used vehicle

If you buy a used vehicle in California, the timing of a smog check depends on whether you are buying from a dealer or a private seller. When buying from a private seller, the seller is responsible for providing a smog check certificate before the sale is complete. That certificate must be dated within 30 days of the sale. If the vehicle is exempt, the seller must provide a written statement saying so.

When buying from a dealer, the dealer handles the smog check and provides the certificate as part of the sale. You do not arrange it yourself.

After you buy the vehicle and transfer the registration into your name, your next smog check will be due at your next registration renewal — which may be up to two years away, depending on when the previous owner's registration was set to expire.

Finding a smog check station and what to expect

Smog checks must be performed at a station certified by the California Bureau of Automotive Repair (BAR). Not every mechanic or service station is certified. You can find a certified station by visiting the official BAR website and searching by zip code, or by searching online for "smog check" in your area and verifying that the station displays its BAR certification.

The test itself takes 10 to 30 minutes. The technician will connect your vehicle to a machine that measures tailpipe emissions. You do not need an appointment at most stations, though some accept them. The cost varies by location and vehicle type but typically ranges from $30 to $70.

If your vehicle passes, you receive a certificate when ready. If it fails, the station will tell you what repairs are needed. You can then take the vehicle to a mechanic, have the repairs done, and return to the same or a different BAR-certified station for a retest. There is no limit on how many times you can retest.

What happens if you fail a smog check

A failed smog check means your vehicle's emissions are above California's limits. Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, or an engine problem that needs repair. The smog station will provide a report listing the specific emissions that failed.

You have 30 days from the test date to have repairs made and return for a retest at a BAR-certified station. If you cannot afford the repairs, California offers the Consumer information Program (CAP), which provides up to $500 toward repairs for low-income vehicle owners. You can learn about CAP through the BAR website or by calling your local air quality management district.

If you cannot get your vehicle to pass within 30 days, you cannot renew your registration. You will need to either complete the repairs and retest, or surrender the vehicle's registration.

Smog checks and vehicle registration renewal important date

Your registration renewal notice will tell you the exact date your registration expires. You need a smog check dated no more than 30 days before that date. If you renew online or by mail through the DMV, the system will not accept your renewal without a passing smog check certificate on file.

If you wait until after your registration expires, you must go to a DMV office in person with your smog check certificate. Driving with an expired registration is a violation, even if you have a smog check and are on your way to renew.

Set a reminder two months before your registration expires so you have time to get a smog check and handle any repairs if needed. This gives you a buffer in case the station is busy or your vehicle fails and needs repairs.

Frequently Asked Questions

Do I need a smog check every year in California?

No. Most vehicles need a smog check every two years at registration renewal time, not annually. Vehicles fewer than four model years old do not need one at all until their first renewal.

Can I get a smog check before my registration expires?

Yes, but it must be dated within 30 days before your registration expiration date. If you get one more than 30 days early, it will not be valid for your renewal and you will need another one.

What if I move out of California — do I still need a smog check?

No. Once you change your vehicle registration to another state, you no longer need California smog checks. You will follow that state's inspection rules instead.

Can I renew my registration without a smog check if my vehicle is exempt?

Yes. Exempt vehicles do not need a smog check to renew registration. You can renew online, by mail, or at a DMV office without one.

What if my smog check certificate gets lost?

Contact the smog station where you had the test performed. They can provide a duplicate certificate or help you retrieve your test results. You will need this to renew your registration.