Definition
A Latin term from the law of actions and pleading meaning "to sum up" or "to account." In legal usage, *computare* refers to the act of reckoning or settling an account between parties. It appears most prominently in the common law writ and action of account (*actio de computo*), where the term describes the formal process by which a defendant was required to render a reckoning of moneys received or held on another's behalf.
The term is inseparable from the phrase *insimul computassent* — "they settled an account together" — which served as a critical averment in the common law action of account and, later, in the action of assumpsit for money had and received. That averment alleged that the parties had mutually struck a balance, and that from this striking of accounts the law implied a promise by the party against whom the balance stood to pay the sum found due.
Common Confusion
*Computare* (to account or sum up) should not be confused with *insimul computassent* (they accounted together), though the two invariably appear in tandem. *Computare* names the act; *insimul computassent* is the pleading averment asserting that the act occurred mutually and resulted in an agreed balance. The legal consequence — an implied promise to pay — flows from *insimul computassent*, not from *computare* standing alone. Older treatises and digests sometimes use the terms interchangeably in headnotes, which can obscure which element is being discussed.
Why It Matters in Research
Researchers encountering *computare* in historical pleadings or treatises should understand that the term is a signpost to a cluster of procedural and substantive doctrines that evolved substantially from medieval to modern practice.
The action of account (*de computo*) was an ancient common law writ compelling a guardian, bailiff, or receiver to render an accounting. *Computare* described the defendant's obligation in that writ. As the action of account fell into disfavor — it was slow, costly, and required two distinct stages — courts of equity absorbed much of its function through the bill for an accounting. Meanwhile, at common law, *insimul computassent* became a count in assumpsit, allowing plaintiffs to recover a settled account balance through a faster, more flexible action. Researchers must therefore trace the term across writ pleading, equity practice, and the assumpsit revolution of the sixteenth and seventeenth centuries to follow its full legal career.
A trap in historical sources: *computare* and *insimul computassent* appear in the same pleading context but do different legal work. *Computare* describes the act of accounting; *insimul computassent* is the averment of an agreed settlement from which a legal promise is implied. Conflating the two can lead to misreading whether a source is discussing compelled accounting or voluntary account-stated.
The term connects the Law Mind corpus entries on account stated, assumpsit, and the old action of account. Researchers interested in the transition from writ-based to assumpsit-based recovery for settled debts should treat *computare* as a gateway term.
Historical Dictionary Support
Anderson's Dictionary of Law gives the foundational definition efficiently: *computare* as "to sum up; to account," paired immediately with *insimul computassent* and its legal effect. Anderson correctly identifies the implied promise theory — that a settled balance against a defendant generates, by operation of law, an obligation to pay — which was the doctrinal bridge that made the account-stated count in assumpsit workable without the cumbersome machinery of the old writ of account.
What Anderson's entry does not develop is the procedural history: the shift away from the original action of account (*de computo*) in which *computare* first appeared as the compelled duty to render accounts, toward its later life as an averment in assumpsit pleading. Historical dictionaries of this period tend to define the Latin term in isolation without charting this migration across forms of action, which is precisely where the doctrinal significance lies.