Definition
A codicil is a formal legal instrument that modifies, supplements, explains, or partially revokes an existing will without replacing it entirely. It functions as an amendment to the will, allowing a testator to update specific provisions — adding bequests, removing beneficiaries, changing executors, or clarifying ambiguous language — while leaving the rest of the original document intact. A codicil must be executed with the same legal formalities required of a will: generally, this means the testator's signature, proper witnesses, and in some jurisdictions, notarization. Upon execution, the codicil is read together with the will as a single testamentary instrument.
A codicil has the additional effect of republishing the will as of the date the codicil is executed. This matters when determining which version of the testator's estate plan controls, and can affect the treatment of property acquired after the will was originally drafted.
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Common Language
Modern common usage (Wiktionary): An addition or supplement modifying any official document, such as a treaty, or any appendix or addition generally.
Historical common usage (Webster's 1913): A clause added to a will.
The ordinary language meaning — any appendix or supplement to a document — is far broader than the legal definition. In law, a codicil is not merely any addition to any document. It is a specific testamentary instrument with mandatory execution formalities and defined legal effects, including republication. Treating a codicil as an informal note or letter of instruction attached to a will would be a serious research error: informal writings lack the execution requirements and do not carry the republication effect.
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Common Confusion
A codicil is sometimes confused with a letter of instruction or a memorandum of personal property. Neither of these is a codicil. Letters of instruction are informal, typically non-binding guides to an executor; memoranda of personal property may or may not be legally operative depending on the jurisdiction and whether the will expressly incorporates them by reference. Only a properly executed codicil has testamentary force. Researchers encountering informal writings attached to a will in historical estate records should not assume they carry codicil status without verifying execution formalities.
A codicil is also distinct from a will republication by re-execution. Both achieve republication, but a codicil does so while expressly preserving the original will; re-execution creates an entirely new will document.
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Why It Matters in Research
Codicils are a persistent research trap in probate records because they are sometimes filed separately from the original will, appear in different deed books or probate registers than the will itself, or were admitted to probate at a different time. Researchers tracing an estate in historical records should always check for separately filed codicils before concluding that a will represents the complete testamentary picture.
The republication doctrine creates a specific research complication: because a codicil republishes the will as of its own date, the effective date of the will for legal purposes may differ from the date on the face of the will document. This can matter for questions involving after-acquired property, the capacity of beneficiaries at the relevant date, and the interpretation of class gifts.
In historical sources, particularly colonial and early American records, codicils were sometimes labeled inconsistently — called "additions," "supplements," or simply written out on the same sheet as the will without separate heading. Researchers using pre-twentieth-century probate records should read entire files carefully rather than relying on document labels alone.
Jurisdictional variation in what constitutes a valid codicil — particularly regarding holographic codicils and witness requirements — affects how historical records from different states should be interpreted. A holographic codicil (handwritten and signed by the testator, without witnesses) may be valid in one jurisdiction and void in another, affecting whether a given document had legal force at all.
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Historical Dictionary Support
The historical dictionaries converge cleanly on the core definition. Black's (both editions) defines the codicil as "a testamentary disposition subsequent to a will" that alters, explains, adds to, subtracts from, or confirms the will by republication — explicitly noting it does not totally revoke the will. Anderson's adds useful framing: a codicil is "annexed to, and to be taken as part of, a testament," reinforcing the point that it does not stand alone.
Bouvier's provides the most historically grounded account, tracing the term to the Roman civil law, where a codicil was defined as an act containing dispositions of property in prospect of death without the institution of an heir or executor. This distinguishes the Roman codicil from a Roman will proper — a distinction that does not carry over cleanly into modern common law, where the functional difference between a will and a codicil is one of sequence and scope, not of whether an executor is named. Researchers using sources grounded in civil law traditions should be alert to this divergence.
Burrill's entry, though brief, confirms the Latin root and the supplement-to-a-will characterization. Webster's 1913 — "a clause added to a will" — is technically narrower than the legal definition and risks understating the codicil's independent formal requirements and its republication effect.
None of the historical dictionaries adequately addresses the republication doctrine or its downstream consequences, which became increasingly significant in nineteenth and twentieth century case law. Researchers relying solely on historical dictionary definitions will have an incomplete picture of how codicils operate in practice.
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Jurisdictional Note
Holographic codicil validity varies significantly by jurisdiction. Roughly half of U.S. states recognize holographic wills and codicils (handwritten and signed by the testator, without witness attestation); others require full witness formalities regardless of whether the document is handwritten. This jurisdictional divide is essential context when evaluating historical estate records, particularly from states with significant civil law influence such as Louisiana, California, and Texas.
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Encyclopedia Cross-Reference
See Law Mind Encyclopedia — Wills and Testamentary Instruments (for execution requirements, republication, and the codicil's role in the broader testamentary scheme); Probate and Estate Administration (for how codicils are filed, admitted to probate, and interact with the original will in estate proceedings).
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