When can a child sit in a booster seat in California?

In California, a child can transition to a booster seat when they are at least 40 pounds and are a minimum of 4 years old. However, the law requires children to remain in a car seat with a harness until they are at least 8 years old or 4 feet 9 inches tall. It's important to ensure that the seat belt fits properly when using a booster seat. Always refer to the manufacturer's guidelines for specific booster seat recommendations.