California requires a smog check every two years for most vehicles, but the exact timing depends on your vehicle's age and registration date

Your smog check schedule is tied to your vehicle registration renewal, not to a calendar date. When you renew your registration with the California Department of Motor Vehicles (DMV), you must have a current smog check certificate on file — one that was issued within 30 days before you submit your renewal. If your registration expires on March 15, you need the smog check done between February 13 and March 15.

Most passenger vehicles registered in California need a smog check every two years. However, vehicles that are eight model years old or newer are exempt from smog checks entirely. Diesel vehicles, motorcycles, and vehicles registered in certain rural counties have different rules. Vehicles that fail smog checks must be repaired and retested before registration renewal is complete.

Key Takeaways

  • Smog checks are required every two years when you renew your vehicle registration, not on a separate schedule.
  • Vehicles eight model years old or newer do not need smog checks, though this exemption ends once the vehicle reaches nine model years old.
  • Your smog check certificate must be dated within 30 days before your registration renewal date to be valid.
  • Diesel vehicles, motorcycles, and vehicles in Alpine, Amador, Inyo, Madera, Mariposa, Mono, and Tuolumne counties follow different smog check rules or are exempt.
  • If your vehicle fails the smog check, you must repair it and pass a retest before the DMV will renew your registration.

How the two-year cycle works with your registration renewal

California does not send you a separate notice for smog checks. Instead, the requirement is built into your vehicle registration renewal. When your registration is about to expire, the DMV sends you a renewal notice. That notice tells you the expiration date — and that is the important date for your smog check certificate to be dated.

You can get your smog check done at any STAR-certified smog station in California. These are repair shops and service stations licensed by the Bureau of Automotive Repair (BAR) to perform smog inspections. You do not have to use a station near your home or where you registered the vehicle — you can test anywhere in the state. The test takes about 10 to 15 minutes and costs between $30 and $50 at most stations, though prices vary.

Once you pass, the station gives you a certificate with the test date on it. You bring that certificate to the DMV when you renew your registration, or you can renew online or by mail if the certificate is already in the system. Many stations now submit results electronically to the DMV, so the certificate appears in your account automatically.

Age-based exemptions: when newer vehicles skip the smog check

If your vehicle is eight model years old or newer, you do not need a smog check. This means a 2017 model year vehicle would be exempt through 2024, then would need a smog check starting with the 2025 registration renewal. The exemption is based on model year, not purchase date, so a 2017 model bought used in 2023 is still exempt until it turns nine model years old.

Once your vehicle reaches nine model years old, it enters the regular smog check cycle. You will need a smog check every two years from that point forward, with no further exemptions based on age. A vehicle that was exempt at eight years old will need its first smog check when it turns nine.

The reasoning behind this exemption is that newer vehicles have emissions control systems that are less likely to fail. Older vehicles, which have had more time for those systems to wear down, are the focus of California's smog program.

Vehicles with different rules: diesel, motorcycles, and rural counties

Diesel vehicles registered in California have their own smog check schedule. Diesel trucks and SUVs that are 1998 or newer need a smog check every two years, just like gasoline vehicles. However, diesel vehicles older than 1998 are exempt. Diesel vehicles also have higher emission limits than gasoline vehicles, so a diesel that would fail a gasoline vehicle's test may still pass.

Motorcycles are exempt from smog checks in California, regardless of age or model year. This applies to all two-wheeled motorcycles registered with the DMV as motorcycles.

Vehicles registered in Alpine, Amador, Inyo, Madera, Mariposa, Mono, and Tuolumne counties are exempt from smog checks. These rural counties have low enough vehicle populations that they are not required to participate in California's smog program. If you move from one of these counties to a county that requires smog checks, your vehicle will need a smog check at your next registration renewal.

What happens if your vehicle fails the smog check

If your vehicle fails the smog check, the station gives you a failed test report. You cannot renew your registration with a failed test. Instead, you must have the vehicle repaired and then take it back for a retest at a STAR-certified station.

You have 30 days from the failed test to get repairs done and pass a retest. If you do not retest within 30 days, you must take the original smog check test again — you cannot use the failed result from 31 days ago. Some stations offer "referee smog checks," which are used when a vehicle has failed multiple times or when there is a dispute about the results. Referee stations are run by the Bureau of Automotive Repair and charge a higher fee, usually $50 to $75.

Once you pass the retest, you get a new certificate dated on the retest date. You then renew your registration with that passing certificate. If your registration renewal important date has already passed, you will owe a late renewal penalty in addition to registration fees.

Timing your smog check to avoid registration delays

The safest approach is to schedule your smog check about two weeks before your registration expires. This gives you time to get the test done, receive the certificate, and submit your renewal to the DMV before the important date. If you wait until the last few days and the vehicle fails, you will not have time to repair and retest.

You can get your smog check done up to 30 days before your registration renewal date. There is no penalty for testing early, and the certificate will be valid as long as it is dated within that 30-day window. Some people test as soon as they receive their renewal notice, which is about 60 days before expiration, but the certificate from that early test will not be valid — you would need to test again within the 30-day window.

If you renew your registration online or by mail, make sure the smog check certificate is in the DMV system before you submit. If you renew in person at a DMV office, bring the physical certificate with you. The DMV will not process your renewal without proof of a passing smog check if your vehicle requires one.

Finding a STAR-certified smog station

The Bureau of Automotive Repair maintains a searchable database of STAR-certified smog stations on its website at bar.ca.gov. You can search by county, city, or zip code to find stations near you. The database shows the station's address, phone number, and hours of operation.

Not all repair shops are STAR-certified. Using an uncertified station means your smog check results will not be valid, and you will have to test again at a certified station. Always verify that a station is STAR-certified before you go. The station should display a STAR certificate in the window or on its website.

Prices for smog checks vary by station and region, but most fall between $30 and $50. Some stations charge extra for retests or for rush service. Call ahead to ask about the price and whether you need an appointment. Many stations accept walk-ins, but calling first can save you a trip if they are busy.

Frequently Asked Questions

Can I renew my registration before I get a smog check?

No. The DMV will not process your registration renewal without a valid smog check certificate on file, unless your vehicle is exempt. If you try to renew online or by mail without the certificate, the renewal will be rejected. You must have the smog check done first, then renew.

What if I move to a different county after I pass a smog check?

Your smog check certificate is valid statewide and does not change based on where you live. If you move from a county that requires smog checks to one that does not (or vice versa), your next smog check requirement is still based on your registration renewal date, not your move date.

Do I need a smog check if I only drive my vehicle occasionally?

Yes, if your vehicle is registered in California and requires a smog check, you need one every two years at registration renewal, regardless of how often you drive it. The requirement is based on registration, not on miles driven or actual use.

Can I get a smog check before my registration renewal notice arrives?

You can get a smog check anytime, but it will only be valid for your registration renewal if it is dated within 30 days before your registration expires. If you test too early, the certificate will expire before your renewal important date, and you will need to test again.

What should I do if a smog station says my vehicle cannot be tested?

Some vehicles cannot be tested at regular STAR stations — for example, vehicles with modified engines or those with outstanding safety recalls. Ask the station why your vehicle cannot be tested. You may need to visit a referee smog station, which can handle more complex cases. Contact the Bureau of Automotive Repair for a referee station near you.