A New Jersey employer with 1 or more employees, and any NJ employer not covered by federal programs must buy workerscomp coverage. Out-of-state companies might need workerscomp coverage if they execute an employment contract in New Jersey or if any work is done in NJ.
Sole Props with zero employees are not required to have a workers comp policy, but may elect to buy a NJ workers comp policy.
Go here to learn more details regardingNew Jersey Workers Compensation Rules