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 South Dakota, the concept of 'nunc pro tunc' is used to retroactively correct clerical errors in court judgments. This legal mechanism allows the court to issue a new or amended judgment that has retroactive legal effect to the date the original judgment was supposed to have been entered. The key aspect of a nunc pro tunc order is that it can only be used to correct clerical mistakes, such as errors in transcription, calculation, or any other mistake that does not involve a substantive legal error. It cannot be used to rectify judicial errors, which are mistakes made in the court's legal reasoning or decision-making process. The purpose of a nunc pro tunc order is to ensure that the written record accurately reflects the court's true intention at the time the original judgment was rendered. South Dakota courts adhere to this principle under their rules of civil procedure, and such corrections are typically made without affecting the rights of the parties from the time of the original judgment.