Definition
A day book is an account book in which merchants, tradespeople, and other business operators record their daily transactions as those transactions occur. It functions as a chronological log of commercial activity — typically sales, services rendered, and deliveries made — entered in the order they happen rather than organized by category or account.
The day book is characterized as a book of original entries: the first written record of a transaction, made contemporaneously or near-contemporaneously with the event itself. This origin character is what gives the day book its evidentiary significance. Because entries are made in the ordinary course of business, at or near the time of the transaction, courts historically recognized the day book as admissible evidence to establish that a sale occurred, that goods were delivered, or that work was performed — particularly in disputes over unpaid accounts.
Common Language
Modern common usage (Wiktionary): Alternative form of "daybook," a book in which daily transactions or events are recorded; a journal or diary.
Historical common usage (Webster's 1913): A tradesman's book in which accounts of daily transactions are kept; a journal.
The common meaning and the legal meaning are closely aligned here, but the legal usage carries a specific evidentiary consequence that ordinary usage does not. In law, the day book's value is not merely organizational — it is its status as a book of original entries that makes it competent evidence in court. A personal diary or general journal does not carry that weight. The legal term imports assumptions about regularity of business practice and contemporaneous recording that determine admissibility.
Why It Matters in Research
Researchers working with commercial, mercantile, or contract disputes in historical sources — particularly pre-twentieth century materials — will encounter the day book as both a procedural artifact and an evidentiary category. Several research traps deserve attention.
First, the term belongs to a cluster of overlapping mercantile bookkeeping records: day book, journal, ledger, waste book, and blotter all appear in historical legal materials, and their distinctions matter for evidentiary purposes. Courts in the nineteenth century drew careful lines between original entry books (which could be admitted) and secondary or copied books (which generally could not stand alone). Knowing which book a witness or party is relying on shapes the analysis.
Second, the evidentiary doctrine surrounding books of account — including the day book — evolved significantly across the nineteenth and twentieth centuries. The traditional common law rule requiring corroboration, the shopbook rule, and eventually the business records exception under modern evidence codes each represent successive frameworks. A researcher reading an older case admitting a day book into evidence should not assume the same result under the Federal Rules of Evidence or their state equivalents without tracing that evolution.
Third, the day book appears in contexts beyond pure contract disputes. Probate proceedings, insolvency and bankruptcy matters, and partnership dissolution cases all may involve day books as evidence of what was owed, what was paid, and when transactions occurred. Researchers in those areas should flag day book references accordingly.
Fourth, in jurisdictions with civil law influence — particularly Louisiana — the rules governing account books and their admissibility developed along distinct lines from common law states. Historical sources from those jurisdictions require separate treatment.
Historical Dictionary Support
Bouvier's Law Dictionary defines the day book cleanly and practically: an account book recording daily transactions, qualifying as a book of original entries, admissible to prove sale and delivery of merchandise or work performed. The entry is brief but accurate in its essentials and reflects the mercantile law context in which the term did most of its legal work.
What Bouvier does not address — and what researchers should supply from other sources — is the conditions under which day book evidence was admitted. Historical courts generally required that the party whose book was offered be unable to produce a witness to the transaction, that the entries appear regular and unaltered, and often that some corroborating evidence exist. The bare definition omits these limitations, which could lead a researcher to overestimate the day book's evidentiary force in a historical proceeding.
No significant divergence exists across available historical dictionary sources for this term. Its meaning was stable and primarily commercial.
Jurisdictional Note
The admissibility of account books including day books was governed by common law shopbook rules that varied in detail by state throughout the nineteenth century. Modern business records exceptions (modeled substantially on Federal Rule of Evidence 803(6)) have largely displaced those rules, but historical litigation involving day books must be analyzed under the evidentiary standards of the forum state at the time of the proceeding.