Failing to show proof of financial responsibility, meaning insurance coverage, is a violation of California Vehicle Code Section 16029. Violating this code could result in fines up to $500 plus penalties, impoundment of the vehicle and suspension of the driver's license. If the vehicle is impounded the owner will have to pay for all storage and tow charges as well.
Per this section of CA law, upon a first conviction, a fine of not less than one hundred dollars ($100) and not more than two hundred dollars ($200) can be assessed. Upon a subsequent conviction, occurring within three years of a prior conviction, a fine of not less than two hundred dollars ($200) and not more than five hundred dollars ($500) may be assessed.
The court in the jurisdiction you received the ticket for being an uninsured motorist will determine the exact amount of the fine. When the court has decided your fine, you can pay in person at the court or by mail normally. Check the ticket, courtesy notice, or court Web site to see whether you can also pay by phone or online. This California court site may allow you to find out your fine amount if you were cited for driving without insurance.