Nunc pro tunc is a Latin expression that translates to “now for then”—meaning to do something now, and for it to have retroactive effect, as if it had been done at a previous time. In the legal context, a judgment nunc pro tunc is a new or changed judgment signed by the court that has retroactive effect to the date the corrected judgment was signed.

The purpose of a judgment nunc pro tunc is to correct a clerical error in the judgment after the court’s authority to change the judgment (its plenary power) has expired. Even a significant change to the original judgment may be accomplished through a judgment nunc pro tunc if it merely corrects a clerical error.

Thus, a judgment nunc pro tunc can generally only be used to correct a clerical error the court made when writing or recording (entering) the judgment the court made (rendered)—and not a judicial error (a substantive error in judicial reasoning) in the judgment. In other words, if the signed judgment inaccurately reflects the true decision of the court, then the error is clerical and may be corrected by judgment nunc pro tunc.

In Massachusetts, the concept of 'nunc pro tunc' is used to retroactively correct clerical errors in court judgments or orders. This legal mechanism allows a court to issue a judgment that has retroactive legal effect to a prior date, typically the date when the original judgment was supposed to have been entered. The purpose of a nunc pro tunc order is not to alter the substantive rights of the parties or to correct judicial errors in decision-making, but rather to ensure that the written record accurately reflects the court's original intent. This can be particularly important when the court's authority to amend its judgment, known as its plenary power, has expired. Massachusetts courts will apply nunc pro tunc orders to correct mistakes such as typographical errors, incorrect dates, or other minor discrepancies that do not involve the merits of the case. It is a tool used to preserve the integrity of the judicial process by ensuring that the official record is consistent with the court's actual rulings.