N.J. Stat. § 54:10A-4.12
Following the enactment of P.L. 2018, c. 48(C.54:10A-5.41 et al.), no penalties or interest shall accrue for underpayment of tax for the provisions of P.L. 2018, c. 48(C.54:10A-5.41 et al.) applying retroactively to tax years beginning on or after January 1, 2017, that create an additional tax liability due to the provisions of P.L. 2018, c. 48(C.54:10A-5.41 et al.), provided, however, the additional payments must be made by either the second next estimated payment subsequent to the enactment of P.L. 2018, c. 48(C.54:10A-5.41 et al.), by December 31, 2018 for tax years beginning on or after January 1, 2017, or by the first estimated payment due after January 1, 2019 for tax years beginning on or after January 1, 2018. In the first tax year that a mandatory combined return is due pursuant to P.L. 2018, c. 48(C.54:10A-5.41 et al.), no penalties or interest shall accrue due to underpayment that may result from the switch from separate returns to mandatory combined returns, and any overpayment by a member of the combined group from the prior tax year will be credited as an overpayment of the tax owed by the combined group, credited toward future estimated payments by the combined group.
N.J.S. § 54:10A-4.12