State laws differ but since the other party's insurance is coming after your son for the claim they paid out on, though he was at fault, your state must allow for your son to be held personally responsible since he did not have insurance on the day of the accident to pay the claim.

Normally when a person is in an accident and the other party is at-fault the person not at fault may file a claim with the at- fault party’s insurance company if they are insured; or, if they have collision insurance on their vehicle, they can have their own insurance company pay for the damages, less your deductible, and the insurer will then usually subrogate against the at-fault party to recover their loss.

For example the Florida Department of Highway Safety and Motor Vehicles (HSMV) states that if you were at fault in an accident with property damage and without insurance you should immediately purchase a personal injury protection and property damage liability (compulsory coverage) insurance policy (the required insurance for the state of FL).

Next the HSMV says to negotiate with each person that sustained property damages to obtain releases for their damages. If the person is insured, you should negotiate with the person's insurance company as the company assumes the rights of compensation since they have reimbursed the insured for their loss. You can obtain a release form from your nearest driver license office.

If you are unable to pay the amount of damages in full, you may pursue a monthly payment agreement. With the insurance coverage and releases or monthly repayment agreements, you will be able to provide them upon notice from the department to avoid unnecessary suspensions of your driver license, tags, and registrations.

Your son may want to seek legal advice to see how best to handle this situation or see if he can negotiate a payment plan with the other party's insurance company to pay on an agreed upon total amount. If he still needs to obtain auto insurance, he can get an affordable car insurance quote here with us.