N.J. Stat. Ann. § 54:1-21

If upon such investigation it shall appear to the Director of the Division of Taxation that the assessment of any property lying in a taxing district or county, including such property of a railroad or canal company, and taxed for a common benefit, is greater than the taxable value thereof, he may, for that purpose, in order to equalize the valuations throughout the territory which contributes to the common burden, reduce the assessment to the amount of the taxable value of the property therein, and at the same time make such increases in the valuation as shall be warranted and as in this article provided. He may further, in any year in which the reduction or increase is made and the tax rate has already been fixed, in order to do justice, equitably equalize the assessment of any piece or pieces of property.