In Missouri, lawsuits are frequently amended to account for newly discovered facts or to correct errors in the initial filing. Under Rule 55.33, the Court is obligated to give permission to amend whenever “justice so requires.” There is a difference, though, between an amended pleading and supplemental pleading.
Also discussed in Rule 55.33, a supplemental pleading is one that sets forth transactions or occurrences or events that happened since the date of the pleadings sought to be supplemented. Courts further must liberally apply the supplemental pleading rules. Thus, Missouri’s Rules draws a fine distinction between an amended pleading and supplemental pleading. The function of the amendment rule is to enable a party to present matters that were overlooked or unknown at the time that the original pleading was filed but without change in the original cause of action. Baker v. City of Kansas City, 671 S.W.2d 325, 329 (Mo. Ct. App. 1984). To the extent a litigant seeks to assert new and different claims, those claims may properly be asserted by way of a supplemental pleading. Based on experience, supplemental pleadings are infrequently utilized. Instead, parties and courts will utilize amended pleadings in part to minimize the number of pleadings on file in a given case.
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