California's New Booster Seat Law From 1 January 2027: Ages 8 to 15 Must Pass the 5-Step Test
From 1 January 2027, AB 435 requires California children aged 8 to 15 to pass a 5-step belt-fit test or stay in a booster. The exact wording, ages and fine.
From 1 January 2027, California's AB 435 says a child aged 8 or older but under 16 may ride with the adult seat belt alone only if the belt passes all five steps of a fit test; otherwise the child must stay in a booster or car seat. Children under 8 still need a car seat or booster unless they are 4 ft 9 in or taller. The base fine is $100 for a first offence.
Short answer: from 1 January 2027, a child in California who is 8 or older but under 16 may ride with the adult seat belt alone only if the belt passes all five steps of a fit test. If it fails any step, the child has to stay in a booster or car seat. Nothing changes for children under 8: they still need a car seat or booster unless they are 4 ft 9 in or taller.
The change comes from AB 435, chaptered on 7 October 2025 as Chapter 434, Statutes of 2025. To check your own child, use the five-step seat belt test.
What the law says
AB 435 amends four sections of the California Vehicle Code: 27315 (seat belts), 27318 (buses), 27360.5 and 27363 (children). The rule for older children is in section 27360.5, which, from 1 January 2027, covers "a child or ward who is eight years of age or older, but less than 16 years of age". Such a child may not be transported "without properly securing that child" in a child seat or booster, "unless the child or ward is properly restrained by a safety belt".
What "properly restrained by a safety belt" means is new. The law spells it out as five requirements, all of which must be met. The section says: "This section shall become operative on January 1, 2027."
The five steps, in the law's words
From section 27360.5(c) as amended:
- "The child or ward is sitting all the way back against the auto seat."
- "The knees of the child or ward bend over the edge of the auto seat."
- "The shoulder belt snugly crosses the center of the child's chest and shoulder, not the child's neck."
- "The lap belt is as low as possible and is touching the child or ward's thighs."
- "The child or ward can stay seated like this for the whole trip."
The same five steps are also written into sections 27315, 27318 and 27363.
8 to 15, or 8 to 16?
Sources disagree. A KPBS report and a California Office of Traffic Safety press template describe the rule as covering children "8 to 16". The statute says "less than 16 years of age", so a child is covered from their 8th birthday up to the day before their 16th. From 16 this section no longer applies. The law firm LCW also reads it as ages 8 to 15.
What changes, at a glance
| Child | Until 31 December 2026 | From 1 January 2027 |
|---|---|---|
| Under 8 | Car seat or booster in the back seat, unless 4 ft 9 in or taller | No change |
| 8 to 15 | Seat belt, or a car seat or booster | Car seat or booster, unless the seat belt passes all five steps |
| 16 and over | Seat belt | No change |
The rest of California's rules (rear-facing under 2 unless 40 lb or 40 in, and the rear-seat rule under 8) are in our booster and car seat laws by state table, which now notes the 2027 change.
The fine
AB 435 does not change the penalties. They are in Vehicle Code 27360.6, which sets a fine of $100 for a first offence and $250 for a second or later offence. A court can reduce or waive the fine for a defendant who is economically disadvantaged and refer them to a community education programme on child passenger safety.
KPBS reported fines of $490. That figure is not in the statute; it is higher than the $100 base fine.
How to do the test
Do it in the car and seat your child actually uses, with the child sitting normally, not posing:
- Sit the child all the way back. If they have to slouch to bend their knees, step 2 fails.
- Look at the shoulder belt from the front. On the neck or slipping off the shoulder fails step 3.
- Check the lap belt sits on the tops of the thighs, not across the stomach.
- Ask honestly whether they will sit like that for the whole trip, including when asleep.
A child can pass in one car and fail in another, because seat depths and belt anchors differ. Test again in each vehicle, and every few months as they grow.
Sources
- California Legislature, AB 435 (2025-26), Chapter 434, Statutes of 2025, bill text read on CalMatters Digital Democracy on 2 November 2026 (the official leginfo page refused our request).
- California Vehicle Code 27360.6, via FindLaw.
- KPBS (15 October 2025). Think your kid's done with a booster seat? New California law says maybe not.
- LCW. AB 435: updated passenger seatbelt restraint requirements.
This page explains the law; it is not legal advice.