Whether you can insure a car without registering it will vary from insurance company to insurance company since underwriting guidelines differ, as do state laws.
In general, insurance companies will request a current registration for three reasons.
First, it helps prove to the company that you have "insurable interest" in a vehicle. A person has an insurable interest in something when loss or damage to it would cause that person to suffer a financial loss or certain other kinds of losses.
Second, some insurance companies require a vehicle to be in a state a set period of time (such as 10 months). Registering a car with the state's Department of Motor Vehicle helps prove that the car is used and garaged within that state.
Third, there are usually state laws that require vehicles to be registered. There may be exceptions for project cars or cars that are being stored. Again, state laws differ regarding these situations.
If you have a car that you want to insure without registering, you can check with various insurance companies to see if their guidelines allow for coverage to be placed on the vehicle. It will depend on state law first and foremost, then the guidelines of the individual insurance company.
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