N.J. Stat. Ann. § 54:4-69

The governing body may by resolution authorize a discount on all such advance payments at a rate not to exceed one-half of one per cent per month for each month for which the advance payments are made. Should the amount so paid for the current year be in excess of the tax or assessment levied, the collecting officer shall, on or before December first of the current year, refund the amount of the excess so paid. Should the payment made be insufficient to equal the assessment for the current year, the difference so due shall be paid or collected as other taxes are collected.