Definition
A plemental bill is a procedural device in equity practice by which new parties, possessing new interests arising from events that occurred after the original suit was commenced, are brought before the court. The plemental bill introduces these new parties and their interests into an existing equity proceeding so that the court can do complete justice among all those now having a stake in the matter.
The defining feature of a plemental bill is the combination of two elements: (1) new parties who were not before the court when the suit began, and (2) new interests that arose after commencement of the suit. Where either of those elements is absent, a different procedural vehicle is ordinarily required.
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Common Confusion
PLEMENTAL BILL vs. SUPPLEMENTAL BILL
These two bills are closely related and frequently conflated, but they serve distinct functions in equity procedure. A supplemental bill is the proper instrument when the same parties and the same interests remain before the court, but something has happened since the suit began that needs to be brought to the court's attention — a change in the state of facts, the death of a party whose interest passes to a known successor, or similar developments that do not disturb the fundamental alignment of parties and interests.
A plemental bill, by contrast, is required when entirely new parties with entirely new interests have come into existence or relevance after the suit was filed. The distinction is therefore between updating the existing proceeding among existing stakeholders (supplemental bill) and enlarging the proceeding to accommodate new stakeholders whose interests simply did not exist, or were not yet implicated, when the suit began.
Rapalje and Lawrence flag this distinction explicitly, noting that the plemental bill "differs from a supplemental bill which is properly applicable to those cases only where the same parties, or the same interests remain before the court." Story's Equity Pleading, which Rapalje and Lawrence cite as authority, treats these as formally separate instruments even though in practice they were sometimes conflated by practitioners and courts.
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Why It Matters in Research
The plemental bill is a creature of classical equity pleading and belongs to a procedural world that has been substantially abolished in American federal practice since the merger of law and equity under the Federal Rules of Civil Procedure in 1938. Researchers working with pre-merger federal equity records, or with state court equity proceedings in jurisdictions that maintained a separate equity practice into the twentieth century, will encounter plemental bills as live procedural documents.
The primary research trap is terminological inconsistency in historical sources. Older reporters and treatises do not always use "plemental bill" as a fixed term of art. Some sources treat it as a subcategory of supplemental bill; others use "supplemental bill" loosely to cover both instruments. When reading pre-merger equity cases, pay close attention to whether the bill actually introduces new parties with new post-commencement interests, because that factual pattern is the functional definition regardless of what label the pleader or court applied.
Rapalje and Lawrence's cross-reference to Story's Equity Pleading (5th ed., §§ 345 et seq.) is the primary historical authority and the correct place to trace the doctrine in depth. Researchers consulting Story directly will find more granular treatment of the circumstances that justify a plemental bill versus those that call for a supplemental bill or an amended bill.
In jurisdictions that have retained or only recently modernized equity procedure — notably some state chancery courts — the distinction between plemental and supplemental bills may still carry procedural significance. State court research in such jurisdictions requires attention to whether local equity rules have preserved, modified, or simply renamed these instruments.
The term also matters for archival and records research. Court dockets and file indexes in pre-merger equity courts sometimes label documents specifically as "plemental bills," and understanding the term is necessary to interpret what the document does and why it was filed at that stage of the litigation.
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Historical Dictionary Support
Rapalje and Lawrence provide a concise but precise definition, keyed to the core distinction from the supplemental bill and grounded in Story's authority. Their entry is notable for its brevity — a single sentence of substance — which reflects the term's relatively narrow technical scope within the broader taxonomy of equity bills. The definition is accurate as far as it goes, but it does not address the procedural mechanics of how a plemental bill was framed, served, or adjudicated, nor does it address what happened when a court found a plemental bill had been used where a supplemental bill was required, or vice versa.
Story's Equity Pleading is the underlying doctrinal source for this distinction, and Rapalje and Lawrence's citation to the fifth edition (§§ 88 and 345 et seq.) is reliable. Researchers needing more than a definition should go directly to Story rather than relying on the dictionary synthesis alone.
No entry for "plemental bill" appears in Black's Law Dictionary early editions under this precise term, which underscores that this was not a universally standardized label even within the historical equity vocabulary. The concept, however, was recognized across American equity practice wherever Story's Pleading was influential.
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Jurisdictional Note
The plemental bill as a distinct procedural instrument is historically specific to equity courts operating under pre-merger practice. In federal courts, the Federal Rules of Civil Procedure (1938) merged law and equity, and modern joinder, amendment, and intervention rules under Rule 19, Rule 20, and Rule 24 now perform the functional work that plemental and supplemental bills once did. State court applicability depends entirely on whether the jurisdiction maintained a separate equity practice and when, if ever, it adopted merged procedure.
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Encyclopedia Cross-Reference
No Law Mind Encyclopedia entry directly addresses equity pleading procedure or the taxonomy of equity bills. The encyclopedia entries surfaced (Bill of Rights incorporation, GI Bill benefits, Bills of Lading) concern unrelated uses of the word "bill" and are not relevant here.
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