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 Missouri, a judgment nunc pro tunc is a legal mechanism used to correct clerical errors in a judgment after the court's authority to amend the judgment has expired. This tool is not intended for substantive changes to the judgment, but rather to ensure that the written record accurately reflects the court's original intent at the time the judgment was rendered. The correction is made retroactively, so the judgment is deemed to have been entered correctly from the original date it was supposed to be recorded. Missouri courts have the authority to issue a nunc pro tunc order to amend clerical mistakes, such as errors in names, dates, amounts, or similar details that do not involve the merits of the case. It is important to note that this remedy cannot be used to alter the substantive ruling of the court or to address judicial errors that might have occurred during the decision-making process.