Definition
A promise, engagement, or stipulation by which a party binds themselves to a particular course of conduct or obligation. The word carries two principal senses in legal usage:
1. Contractual undertaking. Any promise made by one party to a contract, considered independently of the other party's corresponding obligation. Each side of a bilateral agreement may be said to contain an undertaking — a unilateral commitment that does not depend on mutuality to be enforceable. Importantly, an undertaking does not necessarily imply consideration on its face; the word describes the act of promising rather than the legal infrastructure that makes the promise binding.
2. Procedural undertaking. A promise given in the course of legal proceedings — by a party or their counsel — typically as a condition for obtaining a concession from the court. A party seeking an injunction, an adjournment, or some other favorable order may be required to offer an undertaking as security for costs, damages, or compliance. This procedural sense is the dominant one in common law litigation practice, particularly in English and Commonwealth courts.
A narrower historical usage refers to a plaintiff's commitment to bring a cause to trial at the next sitting or assizes — essentially a scheduling pledge enforceable by the court.
Common Language
Modern common usage (Wiktionary): Present participle and gerund of "undertake"; also, any business, project, or enterprise a person engages in.
Historical common usage (Webster's 1913): "That which is undertaken; any business, work, or project which a person engages in, or attempts to perform; an enterprise." Also: "A promise or pledge; a guarantee."
The ordinary English meaning centers on endeavor or enterprise — the thing being attempted. The legal meaning shifts the weight entirely to the promissory dimension: what matters is not the project itself but the formal commitment made, often to a court or counterparty, and the legal consequences that attach to it. A businessperson describing a "major undertaking" is talking about scope of effort; a lawyer offering an "undertaking to the court" is making a binding promise with potential contempt consequences for breach.
Common Confusion
Undertaking is sometimes used loosely as a synonym for guarantee or surety bond, but these are distinct. A guarantee typically involves a third party securing another's obligation; an undertaking is the promisor's own commitment, made in their own right. Similarly, undertaking should not be conflated with covenant, which carries additional formality requirements (historically, a sealed instrument) and distinct remedial rules. In procedural contexts, an undertaking given by counsel is treated as a personal professional obligation, not merely a client instruction — a distinction that matters when enforcement is sought.
Why It Matters in Research
The split between the contractual and procedural senses of undertaking creates a vocabulary trap for researchers working across time periods and jurisdictions. Nineteenth-century English and American case law uses undertaking freely in both senses, often without signaling which is meant. Context — whether the passage concerns a transaction or a court proceeding — is the only reliable guide.
In procedural research, the undertaking as to damages is a critical concept when tracing the history of interlocutory injunction practice. Courts in equity required a plaintiff obtaining an ex parte or interim injunction to undertake to compensate the defendant if the injunction ultimately proved wrongful. This practice is well established in English equity but variably codified in American state courts; researchers should not assume uniform treatment across jurisdictions or time periods.
For contract law research, the Bouvier's formulation — that an undertaking does not necessarily imply consideration — is a useful flag. Sources using this term to describe a promise may be describing something that would not survive modern contract formation analysis without additional facts. Historical pleading records using undertaking as a term of art may be describing assumpsit-adjacent obligations rather than modern bilateral contracts.
Researchers tracing surety and guarantee doctrine should note that Rapalje & Lawrence's entry under undertaking routes to underlease and mortgage-by-underlease, a reminder that older digests sometimes indexed related concepts under counterintuitive headings. Cross-checking under guarantee, surety, and bond is essential when working in that area.
Historical Dictionary Support
The historical sources converge on the promissory core: Black's (both editions), Bouvier's, and Rapalje & Lawrence all define undertaking as a promise, engagement, or stipulation. Black's adds the procedural gloss most explicitly — "a promise given in the course of legal proceedings by a party or his counsel, generally as a condition to obtaining some concession from the court" — and this formulation is the most practically useful for litigation history research.
Bouvier's contributes the important qualification that consideration is not necessarily implied, distinguishing undertaking from a fully executory contract. This signals that historical courts may have enforced undertakings on grounds closer to estoppel or professional obligation than classical contract doctrine.
The Rapalje & Lawrence entry as extracted here is largely devoted to underlease rather than undertaking, suggesting either a misfiled or transitional entry in the source digest. Researchers relying on Rapalje & Lawrence for undertaking doctrine should treat that source cautiously and prioritize Black's and Bouvier's.
None of the historical dictionaries address the modern procedural undertaking as to damages in injunction practice in any developed way — that doctrine is better traced through equity treatises and procedural rules than through dictionary entries.
Jurisdictional Note
The procedural undertaking is most firmly embedded in English and Commonwealth practice, where breach of an undertaking to the court carries contempt consequences as a matter of course. American practice is less uniform: some states codify similar obligations through court rules or bond requirements, while others treat counsel's representations as professional conduct matters rather than enforceable undertakings. Researchers should not transport English equity assumptions about undertakings directly into American state court research without checking local procedural rules.
Encyclopedia Cross-Reference
Law Mind Encyclopedia — Contracts (promissory obligations and consideration)
Law Mind Encyclopedia — Suretyship and Guaranty (distinction from guarantee and bond)
Law Mind Encyclopedia — Civil Procedure: Injunctions (undertaking as to damages in interlocutory practice)