Missouri Revised Statutes

Mo. Rev. Stat. § 509.090 (2026)

Affirmative defenses

✓ current as of May 2026
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  509.090.  Affirmative defenses. — In pleading to a preceding pleading, a party shall set forth affirmatively accord and satisfaction, arbitration and award, assumption of risk, contributory negligence, discharge in bankruptcy, duress, estoppel, failure of consideration, fraud, illegality, injury by fellow servant, laches, license, payment, release, res judicata, statute of frauds, statute of limitations, truth in defamation, waiver, and any other matter constituting an avoidance or affirmative defense.  When a party has mistakenly designated a defense as a counterclaim or a counterclaim as a defense, the court shall treat the pleadings as if there had been a proper designation.

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(L. 1943 p. 353 § 40)

Notes of Decisions
Cited in 69 cases (1 in the last 5 years), 1952–2023 · leading case: Lynch v. Lynch, 260 S.W.3d 834 (Mo. 2008).
Lynch v. Lynch, 260 S.W.3d 834 (Mo. 2008). · cites it 2× “Section 509.090; Agnew v. Union Const. Co.”
TA Realty Assocs. Fund V, L.P. v. NCNB 1500, Inc., 144 S.W.3d 343 (Mo. Ct. App. 2004). · cites it 5× “We first address Tenant’s argument that Landlord’s failure to file a reply admitted Tenant’s affirmative defense based upon section 509.090 RSMo 2000 1 and Rule 55.09.”
Nibler v. Coltrane, 275 S.W.2d 270 (Mo. 1955). · cites it 6× “Section 509.090 RSMo 1949, V.A.M.S. The burden of pleading and proving payment in this action rested upon the defendant.”
Jaycox v. Brune, 434 S.W.2d 539 (Mo. 1968). · cites it 4× “10 (§ 509.090) provides, however, that a party shall plead affirmatively sundry matters constituting affirmative defenses to a preceding pleading.”
Kansas City Stock Yards Co. v. A. Reich & Sons, 250 S.W.2d 692 (Mo. 1952). · cites it 3× “2d 878 ; Section 509.090 RSMo 1949, V.A.M.S.; McGuire v.”
Arditi v. Massachusetts Bonding & Ins. Co., 315 S.W.2d 736 (Mo. 1958). · cites it 3× “Massachusetts did not plead res judicata (see Section 509.090 RSMo 1949, V.A.M.S.; Berghorn v.”
Craig v. City of MacOn, 543 S.W.2d 772 (Mo. 1976). · cites it 2× “Further, since payment is an affirmative defense, § 509.090, RSMo 1969, which appellants did not raise by their general denial to the city’s counterclaim for unpaid charges, nonpayment was properly found on the pleadings.”
Kansas City Power & Light Co. v. Riss, 319 S.W.2d 262 (Mo. Ct. App. 1958). · cites it 7× “There is no claim that ejectment would lie in the instant case.”
O'Leary Ex Rel. O'Leary v. Illinois Terminal R.R., 299 S.W.2d 873 (Mo. 1957). · cites it 4× ““Plaintiff also urges that section 509.090 RSMo 1949, V.A.M.S., which makes contributory negligence an affirmative defense, ‘is not affected by the procedural law of the locale of the occurrence.”
McDougal v. McDougal, 279 S.W.2d 731 (Mo. Ct. App. 1955). · cites it 3× “Section 509.090 RSMo1949, V.A.M.S. A motion to quash an execution for alleged invalidity of the judgment on which it is based constitutes a collateral attack on the judgment [Gary Realty Co.”
Se-Ma-No Elec. Coop. v. City of Mansfield, 321 S.W.2d 723 (Mo. Ct. App. 1959). · cites it 6× “s court cannot consider the issue of res judicata; that under the record we can consider only the question whether the present petition states a cause of action; that the defense of res judicata is an affirmative defense and must be specifically pleaded and proved; that there is…”
Dugan v. Trout, 271 S.W.2d 593 (Mo. Ct. App. 1954). · cites it 4× “23], as to the sufficiency of defendant’s amended answer to state a legal defense and as to whether a submissible case was made on defendant’s plea of failure of consideration, which was an affirmative defense [Section 509.”
Annotations are extracted automatically from the opinions in the Syfert caselaw corpus and ranked by authority, recency, and treatment. Dots show Syfertize treatment of the citing case itself.