Many states require trailer to be registered; however, there are no states which mandate trailer insurance on personal. recreational trailer. This is not true for commercial utility trailer that haul equipment and machinery and transport goods and supplies to various destinations.
If you are using your trailer for business purposes, you must have insurance and valid registration with the state motor vehicle department.
Utility trailers which are being used for non-business purposes are covered by the same coverage that is insuring the tow vehicle. A utility trailer used for business purposes requires a commercial auto insurance policy.