In almost all states, having a valid auto insurance policy is required. Even if you reside in one the few states that do not specifically demand you have an insurance policy, all states also have financial responsibility laws. This means that even if you live in a state that does not require a liability insurance policy, you still need to have sufficient assets to pay claims arising if you are the cause an accident. This does allow one with ample assets to “Self Insure”, though this is an extremely rare occurrence.
Overwhelmingly one who has enough money to set aside to “Self Insure” chooses not to purchase auto insurance.
If you don’t have adequate assets, you must buy at least the state minimum amount of insurance. For example of the state minimum limits for auto liability insurance. In Illinois the minimum limits are 20/40/15 or a limit of $20,000 for one individual, up to $40,000 coverage combined for all persons injured in an accident, and $15,000 coverage for property damage. In Indiana the limits are 25/50/10 In Mississippi they are 25/50/15.