A recent Missouri case holds that a party seeking to enforce a prenup must raise the issues in a pleading. Failure to do so prevents the court from enforcing the prenup. Homan v. Holman, which can be found here.
In pleading to a preceding pleading, a party shall set forth all applicable affirmative defenses and avoidances . . . . A pleading that sets forth an affirmative defense or avoidance shall contain a short and plain statement of the facts showing that the pleader is entitled to the defense or avoidance.[(FN3)]
"An affirmative defense is waived if the party raising it does not plead it." In re Estate of Kilbourn, 898 S.W.2d 583, 586 (Mo.App. 1995).
Based on the foregoing, we determine the trial court abused its discretion in permitting Husband to introduce the Agreement at trial because Husband failed to assert the Agreement as an affirmative defense in his pleadings. It has long been held that "[m]atters seeking avoidance of a valid contract are affirmative defenses and must be set out in the pleadings." Id. The terms of the Agreement clearly provide "'additional facts [other than the statutory considerations of section 452.300] that permit [Husband] to avoid the legal responsibility alleged'" by Wife, i.e., that there was marital property to be divided. Smith v. Thomas, 210 S.W.3d 241, 244 (Mo.App. 2006) (quoting Mobley v. Baker, 72 S.W.3d 251, 257-58 (Mo.App. 2002)). A party that fails to raise an affirmative defense in his pleadings, waives that issue at trial. In re Estate of Kilbourn, 898 S.W.2d at 586.