N.J. Stat. § 54:4-63.3
When any parcel of real property has been sold by any municipality as not needed for public use, and the deed has been delivered between January 1 and October 1 in any year, or when any parcel of real property contains any building or other structure which has been erected, added to or improved after October 1 and completed between January 1 and October 1 following, the assessor shall, after examination and inquiry, determine the taxable value of such parcel of real property as of the first of the month following the date of delivery of such deed, or of such completion, and if such property was not assessed as of October 1 preceding or, if such value so determined exceeds the assessment made as of October 1 preceding, the assessor shall enter an assessment, as an added assessment against such parcel of real property, in the "Added Assessment List, 19," which assessment shall be determined as follows: by multiplying the amount of such assessment or such excess by the number of whole months remaining in the calendar year after the date of delivery of such deed, or of such completion, and dividing the result by 12.
N.J.S. § 54:4-63.3