An additur is an increase in the amount of damages awarded in a civil case. Additurs are not allowed in all legal systems, and in those where they are, they are issued by the judge, usually with the goal of adding punitive damages to a case. The purpose of an additur is to sidestep the need for an appeal and retrial in the event that a plaintiff feels the damages awarded in a case were not sufficient. The defendant does not have a say in whether the damages are awarded, but can opt to proceed to retrial instead and hope to get a favorable treatment from the jury.
Judges can decide to increase the damages with an additur in a case where the jury awarded an amount that seems unfairly low, given the circumstances of the case. This can come up in cases where the defendant's actions are thought to be particularly bad, or when the judge wants to send a clear message to people considering similar actions that they will be heavily penalized. The additur acts as a punishment and a warning.
If a plaintiff indicates an intent to pursue a retrial in cases where the damages are not felt to be fair, the judge can decide to issue an additur to the damages awarded by the jury in order to avoid the retrial. The defendant can weigh the options of accepting the higher damage award or proceeding to retrial. Since juries can be harsh during retrials, the defendant may opt to take the higher award rather than risking the outcome of another jury decision.
Once the outcome of the case is finalized, the defendant is expected to pay or make arrangements to pay, if it is not possible to make a single lump sum payment to settle the case. If the defendant does not respond, court can be convened again to compel the defendant to pay, using a variety of means including garnishment of accounts and wages to satisfy the terms handed down by the judge and jury.
By contrast, a remittitur involves reducing the damages awarded by a jury. Judges are authorized to do this when they feel the amount awarded is unreasonable or of questionable legality. Reductions in the amount of damages are generally permitted in most legal systems, while additurs tend to be less permissible. In the United States, for example, federal judges cannot issue an additur, but they can issue a remittitur.