Beginning on January 1, 1984, New Jersey’s treatment of 401(k) Plan contributions changed. After that date, employee contributions to 401(k) Plans were no longer included in taxable wages when earned. If you made contributions to a 401(k) Plan before January 1, 1984, your distribution will be treated differently than if all the contributions were made after this date.
See page 32 here:
https://www.state.nj.us/treasury/taxation/pdf/pubs/tgi-ee/git1.pdf
