Whether you’re buying, selling, or registering a used vehicle in California, understanding the state’s smog check requirements is crucial. California has some of the strictest emissions laws in the country, non-compliance can lead to DMV rejections, fines, or even being unable to legally register a car.
🔍 WHAT IS A SMOG CHECK?
A smog check (also known as a smog test or emissions test) is a state-mandated inspection to measure a vehicle’s emissions output. The goal is to ensure that vehicles do not exceed federal and state air pollution limits. It’s part of California’s Vehicle Inspection Program, overseen by the Bureau of Automotive Repair (BAR).
WHY DOES CALIFORNIA REQUIRE SMOG CHECKS?
California suffers from some of the worst air pollution in the U.S., particularly in high-traffic metro areas like Los Angeles, Riverside, and San Bernardino. To combat this, the California Air Resources Board (CARB), in partnership with the Department of Motor Vehicles (DMV) and Bureau of Automotive Repair (BAR), enforces strict emissions testing to ensure cars meet clean air standards.
Goals of the Smog Program:
- Detect high-polluting vehicles
- Reduce greenhouse gas emissions (NOx, CO, HC)
- Ensure compliance with federal EPA and California regulations
- Protect public health and the environment
WHEN IS A SMOG CHECK REQUIRED?
In California, a smog check is required when:
1. Selling a Used Car (Private or Dealer Sale)
If you are selling a gas-powered vehicle that is more than 4 model years old, you are legally responsible for providing a valid smog certificate at the time of sale.
- California Vehicle Code §24007(b)(2): “The seller is required to provide evidence of compliance with the smog requirements at the time of delivery.”
- The smog certificate is valid for 90 days
- If the vehicle fails, you must repair it before selling (or disclose and negotiate an “as-is” sale if the buyer agrees)
2. Registering a Used Car Purchased from Out of State
- Required even if the car passed emissions in another state
- Must be tested and pass California’s stricter emissions standards
- Required for gasoline, diesel, and hybrid vehicles (with some age exceptions)
3. Renewing Vehicle Registration
- Most vehicles must pass smog every 2 years (biennial inspection)
- You’ll receive a DMV renewal notice stating whether a smog check is required
🔎 If you’re buying or selling a used car, a smog check is usually mandatory — unless it meets one of the exemptions (listed below).
🚫 SMOG CHECK EXEMPTIONS
Not all used cars are required to undergo a smog inspection. Here are the major exemptions:
✅ Age-Based Exemptions:
Gasoline vehicles under 4 model years old
Exempt at time of sale and renewal (but buyer must pay $8 smog abatement fee)
Diesel vehicles model year 1997 and older
Exempt
Vehicles manufactured before 1976
Permanently exempt (considered “classic”)
✅ Fuel-Type Exemptions:
- Fully electric vehicles (EVs)
- Motorcycles
- Natural gas vehicles over 14,000 lbs. GVWR
- Trailer-type vehicles
⚠️ Hybrid vehicles are NOT always exempt. Smog checks may be required for hybrids that are older than 8 model years, depending on BAR regulations. Even though they are not always exempt, hybrid vehicles are still a smart choice.
AREAS THAT REQUIRE SMOG CHECKS (ENHANCED AREAS)
California doesn’t require smog checks in every county. However, most populated areas do. These are known as Enhanced Smog Check Areas and include:
- Los Angeles County
- Orange County
- Riverside County
- San Bernardino County
- Santa Clara County
- San Diego County
- Sacramento County
SMOG CHECK PROCESS
1. Find a Licensed Smog Station or STAR Station
- Search for you local licensed Smog or STAR Station here
2. Take Your Car in for Inspection
- Inspection includes tailpipe emissions, onboard diagnostics (OBD), and visual inspections
3. Pass or Fail
- If passed, the smog certificate is electronically sent to DMV
- If failed, repairs must be made and retested
MORE: Find out when’s the best time to buy a used car
⭐ STAR STATION
Some vehicles are randomly directed to STAR-certified stations. These are state-monitored smog check facilities held to higher performance and accuracy standards.
STAR Station Requirements Apply If:
- Your DMV notice says “SMOG Check Required at STAR Station”
- Your vehicle has a high-emissions profile or has failed in the past
- You’re registering an older out-of-state car
FAILING THE SMOG TEST
If a car fails, it cannot be registered until it passes.
Options After a Failed Test:
- Repair the vehicle at a certified emissions repair station
- Apply for the Consumer Assistance Program (CAP) through BAR:
- Up to $1,200 in repair assistance for low-income consumers
If a car cannot pass the smog test, it’s a clear sign that it might be time to replace your vehicle.
💸 SMOG CHECK COST IN CALIFORNIA
The cost of a smog check can vary based on location, vehicle type, and station. On average:
- Standard Smog Check: $40 – $70
- STAR Station Smog Check: $60 – $100
- Certificate Fee (DMV): $8.25 (added after passing)
💡 Tip: If your registration renewal notice says “SMOG Certification Required at STAR Station,” you must go to a state-designated STAR-certified facility.
CHECKING SMOG TEST HISTORY OF A USED VEHICLE
Before buying a used car, you can check its smog test history through the BAR Vehicle Test History tool.
All you need is the vehicle’s VIN or license plate number.
TIPS TO AVOID COSTLY MISTAKES
- Never complete a private sale without confirming the smog certificate
- Always check the DMV title transfer page for updated smog requirements
- Don’t rely on past tests — the certificate must be recent (90 days)
- Avoid buying cars that aren’t California emissions-compliant if coming from another state
FINAL THOUGHTS
Whether you’re upgrading your car, buying a used vehicle for the first time, or relocating to California, understanding smog check rules is critical. California’s strict air quality laws are enforced through this process, and failure to comply can delay your ability to drive legally.
Don’t cut corners. Take the time to verify smog status, get a proper inspection, and make sure your sale or purchase goes smoothly.