New Jersey Department of Banking and Insurance (DOBI), the insurance regulator for NJ, has a guide for auto insurance that states that New Jersey law requires insurers to offer discounts for drivers who have completed a Defensive Driving course approved by the New Jersey Motor Vehicle Commission.

Successful completion of an approved motor vehicle defensive driving course renders licensees eligible for automobile insurance rate reduction pursuant to N.J.S.A. 17:33B-45.1 and motor vehicle point reduction in accordance with N.J.S.A. 39:5-30.9.

Since January 1996, when N.J.S.A. 17:33B-45.1 was signed, NJ requires insurance premium discounts for drivers who successfully completed an approved Driver Safety course. It goes on to state that all insurance companies writing private passenger policies in New Jersey, would apply a minimum of five percent discount to the base rate for Bodily Injury Liability, Property Damage Liability, Personal Injury Protection and Collision coverages.

The rate reduction is available for three years or until a driver accumulates four (4) motor vehicle points or loses his/her license.

Discounts apply to private passenger automobiles, with only one discount per vehicle. If the policy insures two or more vehicles, the discount applies to the vehicle principally operated by the person who completes the course. 

With some insurance companies this discount is called an accident prevention discount and comes with certain other requirements so you would need to adhere to. To find out how much the discount would affect your rates or cause them to be reduced by you would need to speak to your insurance agent.

The NJ DOBI notes that to find an approved school near you, call 1-888-486-3339.