Duhaime's Law Dictionary

Exceptio Non Adimpleti Contractus Definition:

Latin: exception of a non-performed contract.

An exception or defense available in Roman law, that a person who is being sued for non-performance of contractual obligations can defend themselves by proving that the plaintiff did not perform their side of the bargain.

Ryan articulated the maxim as follows:

“Exceptio non adimpleti contractus ... the right to refuse to perform one’s obligations under a reciprocal contract unless or until the other party dos so.

“No performance is due to one who has not himself performed.”

Not all civil jurisdictions have incorporated this maxim of Roman law into their civil code. Obviously, such a maxim of law can result in a never-ending circle; both parties to a contract enabled, legally, to await the performance of the other before performing themselves.

Nonetheless, the maxim found a home in the 1900 German Civil (at s. 320) but not in the French Civil Code of 1804.

Section 320 of the German Civil Code:

“Plea of Unperformed Contract: Whoever is bound by a mutual contract may refuse to perform his part until the other party has performed his part, unless the former party is bound to perform his part first.”


  • Forrester, I., and others, The German Civil Code (South Hackensack, New Jersey: Fred B. Rothman & Co., 1975)
  • Roland, H. and Boyer, L., Locutions Latines du Droit Francais, 3e ed. (Paris: Libraire de la Cour de cassation, 1993), page 119-120
  • Ryan, K. W., An Introduction to The Civil Law (Sydney: The Law Book Co. of Australia, 1962), pages 82-83

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