California’s 2026 car seat law is changing, and if you have a child between the ages of 8 and 12, you need to act now. On October 14, 2025, Governor Gavin Newsom signed Assembly Bill 435 (AB 435) into law, introducing stricter requirements for how children must be properly and safely restrained in vehicles.
While the existing law remains in effect through 2026, the new standards taking effect on January 1, 2027, will change booster seat rules statewide. Understanding these changes now is critical to both your children’s safety and your compliance with the California Vehicle Code.
What is California AB 435?
AB 435 addresses a dangerous safety gap: the so-called “forgotten years” between ages 8 and 12, where children often outgrow boosters but are still too small for adult seat belts to fit properly.
Under the new California’s 2026 car seat law, children must pass a 5-Step Test before transitioning to a standard seat belt.
The most significant changes under the California 2026 car seat law include:
- Age Increase: The threshold for mandatory child restraint (car seats or boosters) in the rear seat effectively moves from under age 8 to under age 10.
- The 5-Step Test: Children ages 10 to 16 may use a standard seat belt only if they pass a specific 5-point safety test.
- The California’s 2026 car seat law reinforces that children should remain in the rear seat until age 13,
- aligning state law with NHTSA safety recommendations.
The Mandatory 5-Step Test
Starting in 2027, age and height (the traditional 4’9″ rule) will no longer be the sole factors for seat belt use. Under the new California’s 2026 car seat law, AB 435, a child is only “properly restrained” by a seat belt if they meet all five of these physical criteria:
- Back: The child sits all the way against the vehicle’s seatback.
- Knees: The child’s knees bend comfortably over the edge of the vehicle seat.
- Shoulder: The shoulder belt snugly crosses the center of the chest and shoulder (not the neck or face).
- Lap: The lap belt fits low and tight across the upper thighs or hips (not the stomach).
- Behavior: The child can maintain this seated position throughout the trip.
If a child fails even one step, they must remain in a belt-positioning booster seat. This test is now the legal standard in California. Therefore, parents and caregivers should begin applying it today, even before the 2027 enforcement date.
Important Deadlines and Penalties Under AB 435
- Implementation Date: The new requirements of AB 435 become legally enforceable on January 1, 2027.
- Fines: Violations are classified as infractions. Under the updated code, drivers can face fines starting at $20 for a first offense, with subsequent fines increasing to $50. In some jurisdictions, total costs, including court fees, can exceed $400.
- The California’s 2026 car seat law means compliance is not just a matter of traffic tickets; it can also affect a legal claim if an accident occurs. Children 8 and older (or 4’9″ tall) may use a seat belt, though experts strongly advise using the 5-Step Test voluntarily starting today.
Why the California’s 2026 Car Seat Law Matters for Personal Injury Claims
In California, car seat compliance is not just a matter of traffic tickets; it can impact a legal claim if an accident occurs. California operates under pure comparative negligence.
This means that if a child is injured in a crash caused by another driver, the defense may argue that the parent’s failure to properly restrain the child according to AB 435 standards contributed to the severity of the injuries.
However, even if a child was improperly restrained, families may still be entitled to recover significant damages from the at-fault driver.
The bottom line: the stricter you are about following the California’s 2026 car seat law, the stronger your legal position if the unthinkable happens.
Safety Resources for Parents
The California Highway Patrol (CHP) offers free child car seat inspections and installations. We strongly recommend that all parents of children aged 8–12 have their child evaluated by a certified technician to determine whether their child is truly ready for a seat belt under the new California’s 2026 car seat law.
About Sasooness Law Group
Sasooness Law Group is a premier California personal injury firm with a proven track record of recovering over $100 million for injury victims. We serve families across Los Angeles, the San Fernando Valley, and all of Southern California.
Contact Sasooness Law Group today for a free consultation, or call: (888) 922-8339.
Disclaimer: The information provided in this blog post is for general informational purposes only and does not constitute legal advice. This does not create an attorney-client relationship. Laws are subject to change and may vary based on the specific facts of a case.