Definition
An assumpsit (Latin: "he undertook" or "he promised") is, in its primary sense, a promise or undertaking founded on consideration — oral or written, but never under seal. In its procedural sense, assumpsit is a common-law form of action brought to recover damages for breach or non-performance of such a promise. The action lies on both express and implied contracts and was historically distinguished from debt (which required a liquidated sum) and from covenant (which required a sealed instrument).
1. As a promise or contract: Any parol agreement — express or implied — by which one party undertakes to do some act or pay something to another for that other's benefit, supported by consideration, and not executed under seal.
2. As a form of action: A civil action at common law, classified among the "actions upon the case," by which the injured party sought damages proportional to the loss suffered from the breach of a parol contract. In older sources it appears as "action upon the case upon assumpsit."
Common Language
Modern common usage (Wiktionary): A promise or undertaking, express or implied, founded on consideration; or the action to recover damages for breach of such a promise.
Historical common usage (Webster's 1913): A promise or undertaking founded on a consideration, oral or in writing but not under seal; also the action to recover damages for breach or nonperformance of such a promise.
The gap between common and legal meaning here is procedural rather than definitional. Both usages share the same core concept, but the legal meaning carries an entire architecture of pleading rules, writs, subtypes, and jurisdictional distinctions that Webster's and Wiktionary flatten into a sentence. A researcher encountering "assumpsit" in historical legal sources needs to know which sense — promise or action — is operative, and which subtype of action is at issue.
Common Confusion
Assumpsit is frequently confused with debt and covenant because all three are common-law contract actions. The distinctions matter enormously in historical sources:
- Debt required a liquidated, ascertained sum certain; assumpsit originally lay for an unascertained sum, though later it could be brought for a fixed sum as well.
- Covenant required the contract to be under seal; assumpsit required the opposite — the contract must be a parol agreement, not under seal.
- Trespass on the case is the parent category: assumpsit is a species of case, and older sources use "action upon the case upon assumpsit" interchangeably with "assumpsit."
Researchers also conflate the two primary subtypes (see below). Indebitatus assumpsit rests on an implied promise and was the vehicle for quasi-contractual recovery; special assumpsit rests on an express promise and requires more particular pleading.
Recognized Forms
/SUBTYPES
1. Special Assumpsit: Founded on an express promise. The declaration must set out the specific terms of the agreement. Used when the parties' actual words and undertakings are the basis of the claim.
2. General (Indebitatus) Assumpsit: Founded on an implied promise — the law implies a promise to pay from the circumstances (e.g., goods sold and delivered, money had and received, work and labor done). Indebitatus assumpsit was the procedural engine of quasi-contract doctrine and the historical precursor to modern unjust enrichment claims. It was brought "for the most part on an implied promise," and the counts within it (money had and received, quantum meruit, account stated, etc.) each addressed a distinct factual pattern.
Why It Matters in Research
Assumpsit is a term that requires era-awareness. It appears in three distinct research contexts, and conflating them produces errors:
First, as a pleading form, assumpsit is largely abolished in modern American and English practice, replaced by notice pleading and the general civil complaint. A researcher encountering assumpsit in post-1938 federal sources (post-Federal Rules of Civil Procedure) or post-Judicature Acts sources in England is reading either historical quotation, a surviving equity jurisdiction, or an anachronistic usage.
Second, indebitatus assumpsit is the direct ancestor of modern quasi-contract and unjust enrichment doctrine. When tracing the development of restitution law, researchers must follow assumpsit through its common-law counts. The money-had-and-received count under indebitatus assumpsit is the clearest line of descent.
Third, jurisdictional survival varies. Some American states retained common-law forms of action well into the twentieth century, and assumpsit remained a live pleading category in those jurisdictions long after others abolished it. Researching a nineteenth-century state court decision requires checking whether that jurisdiction had reformed its pleading rules.
Corpus trap: The word "assumpsit" in a historical case may refer to the promise itself, the action, or be used as a shorthand for a count within a declaration. Read the surrounding pleading context carefully before concluding what is at issue.
Historical Dictionary Support
The historical dictionaries converge on the core definition but illuminate different facets. Black's (both editions) leads with the Latin meaning and emphasizes the promise as the foundation: "a promise or engagement by which one person assumes or undertakes to do some act or pay something to another." Burrill goes further into the pleading structure, grounding assumpsit as "the name of a civil action given by law to the party injured by the breach or non-performance of a parol contract legally entered into" and specifying that damages are proportional to loss — useful for understanding the remedy side. Bouvier draws the sharpest distinctions, explicitly contrasting assumpsit with debt (no liquidated sum required) and covenant (no sealed instrument required), and situating it among the actions upon the case. Anderson adds the useful historical note that assumpsit "originally lay for an unascertained sum, but may now be brought for a fixed sum" — a signal of doctrinal evolution during the nineteenth century as courts loosened the debt/assumpsit boundary.
What the historical dictionaries underemphasize is the quasi-contractual dimension of indebitatus assumpsit. The entries gesture at implied promises but do not develop the connection to unjust enrichment that modern legal historians treat as the action's most consequential legacy.
Jurisdictional Note
Common-law states that retained code pleading (rather than adopting notice pleading early) kept assumpsit alive as a recognized action into the mid-twentieth century. In England, the Judicature Acts (1873–1875) effectively merged assumpsit into the general civil action, but the underlying substantive distinctions between express and implied contract survived the procedural merger. Researchers using Canadian sources should be attentive to provincial variation in the timing of pleading reform.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Actions on the Case; Quasi-Contract and Unjust Enrichment; Common Law Pleading Forms.