California’s 2027 Booster Seat Law: What AB 435 Actually Changes

Parents often hear a simple rule: after a child turns eight—or reaches 4 feet 9 inches—the child can leave the booster behind. That shortcut misses the way a belt fits in a particular car. A shoulder belt at the neck or a lap belt across the stomach is not the fit the law is trying to achieve. California Assembly Bill 435, chaptered in 2025, changes the legal definition of being “properly restrained by a safety belt” for children from age eight until their 16th birthday. The change becomes operative January 1, 2027; it is not yet the operative rule as of this article’s October 2026 publication.

What is California’s five-step seat-belt test?

AB 435 adds the following five criteria to Vehicle Code § 27360.5(c). To ride with a seat belt alone, a child age 8 through 15 must meet all five:

1. The child sits all the way back against the vehicle seat.
2. The child’s knees bend over the edge of the vehicle seat.
3. The shoulder belt crosses snugly over the center of the chest and shoulder, not the neck.
4. The lap belt is as low as possible and touches the thighs.
5. The child can maintain that seated position for the whole trip.

These are the bill’s criteria paraphrased for readability—not a height-only or age-only cutoff. Fit may differ between a back seat and another vehicle, so check the actual seat and belt the child will use. A booster can help position a vehicle belt correctly when the unboosted child does not meet the test; follow the restraint manufacturer’s height and weight limits and installation instructions. The law uses the broader term “appropriate child passenger restraint system,” rather than mandating one booster model for every child.

What changes, and what stays the same?

For children under eight: Vehicle Code § 27360 continues to generally require an appropriate child passenger restraint system in a rear seat, with the existing exceptions in § 27363. AB 435 retains the exception allowing a child under eight who is at least 4 feet 9 inches tall to use a properly fitting safety belt instead of a child restraint; it adds the five-step definition for belt fit in the replacement § 27363 effective in 2027. Other medical, emergency, vehicle-configuration and front-seat exceptions are fact-specific. The current rear-facing requirement for children under two, subject to the statutory height/weight exception and manufacturer limits, also remains important.

For children eight through 15: The replacement § 27360.5 allows an appropriate federally compliant child passenger restraint or a belt that satisfies all five steps. A birthday alone does not pass the test. The subsection also says its driver-specific prohibition does not apply when a parent or legal guardian is present as a passenger and is not driving; that exception does not make an improperly fitted belt safe.

For passengers 16 and older: Different seat-belt provisions apply. AB 435 also amends other vehicle and bus belt definitions; this guide focuses on children in ordinary passenger vehicles. Do not use this article as a substitute for the applicable statute for a bus, taxicab, or other special vehicle.

How can a family check fit before January 2027?

• Seat the child all the way back in the actual car and position. Check knees, shoulder-belt placement, lap-belt placement and whether the position lasts for an ordinary trip.
• If any element fails, use a correctly installed, appropriate child restraint that fits the child and vehicle. Do not put the shoulder belt behind the back or under an arm to avoid neck contact.
• Review the car seat and vehicle manuals. A certified child passenger safety technician can help with installation and fit; the California Highway Patrol child safety seat page directs families to local CHP offices for assistance. That CHP page describes the law currently in effect and may not yet reflect the 2027 transition.

A car-seat decision is about protection first, not avoiding a ticket. Claims that AB 435 automatically imposes a particular all-in fine or a point on every driver’s record should not be accepted without checking the applicable violation and assessment schedule. This article makes no such promise.

What if a child is hurt in a California crash?

The first priority is medical care. If it is safe to do so, preserve photographs of the vehicle’s seating positions, seat belt, installed child restraint and labels; keep the restraint and its manual, and record the child’s approximate height and the seat used. Obtain the collision report and identify witnesses. Do not discard a restraint involved in a collision before consulting the manufacturer’s replacement guidance and any insurer or lawyer handling evidence preservation.

A restraint-law violation is not automatic civil liability. A claim may involve another driver’s driving, causation, comparative fault, injury severity and the actual facts of the crash. California’s Evidence Code § 669 sets conditions for a presumption based on violation of a safety statute; it does not decide fault merely because a child used a particular restraint. Nor does a parent’s choice by itself erase a child’s potential claim against a negligent driver. An attorney can evaluate the collision and any preservation or deadline issues in context.

Frequently asked questions

Sources and further reading

• AB 435, chaptered October 7, 2025 (Chapter 434, Statutes of 2025), especially sections adding Vehicle Code §§ 27360.5 and 27363 with a January 1, 2027 operative date. The California Legislature’s direct site was returning an access challenge when this article was prepared; the chaptered bill text was reviewed through this legislative mirror.
• California Legislature AB 435 bill page (official source, if accessible).
• California Highway Patrol, Child Safety Seats (current-law guidance and inspection referral).
• Vehicle Code § 27360 and § 27363 (mirrors of current pre-2027 code; not the replacement 2027 text).

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