Rule 15.Amended and supplemental pleadings

Lawsuits change shape as facts emerge, so Rule 15 gives parties room to fix or expand their pleadings without starting over. Early in a case, a party can amend a complaint, answer, or other pleading once without asking anyone's permission, so long as it happens within 21 days of filing or within 21 days after the other side responds. Once that window closes, the party needs the opposing side's written consent or the court's permission, and the rule tells judges to grant that permission freely when doing so serves justice rather than punishing a party for an imperfect first draft.

The rule also addresses amendments that come later, mid-trial or after the fact. If evidence at trial strays outside what the pleadings cover, the court can allow the pleadings to catch up, and when both sides go along with trying an unpleaded issue, the pleadings are treated as if they always included it. Amendments that add a claim, correct a party's name, or raise a new theory can relate back to the date of the original pleading, which matters when a statute of limitations would otherwise bar the claim, provided the new matter grows out of the same conduct or transaction. Separately, a supplemental pleading lets a party add facts about events that happened after the original pleading was filed, keeping the case current without forcing a new lawsuit.