Codicil (will)

A codicil is a testamentary document similar but not necessarily identical to a will. In some jurisdictions, it may serve to amend, rather than replace, a previously executed will. In others, it may serve as an alternative to a will. In still others, there is no recognized distinction between a codicil and a will.

The concept of a testamentary document similar to but distinct from a will had its origins in Roman law. In the pre-classical period, a testator was required to name an heir for a will to be valid (heredis institutio). Failure to name an heir or failure to follow the proper formalities for naming an heir would result in an estate divided by the rules of intestacy. However, a testator was also able to create a fideicommissum, a more flexible and less formal indication of the testator's intent which could have the effect of transferring part or all of an estate after death, although with fewer rights to the beneficiary than those of a named heir.

A codicillus (diminutive of codex) was a written document subject to less stringent formal requirements than a will (testamenta) that, in its initial use, could supplement or change an existing will, provided the codicil was specifically mentioned (confirmed) in the will. However, if the will did not confirm the codicil, all directives in the codicil were considered fideicommissa. Furthermore, a will that did not name an heir could be considered a codicil. Thus, where a testator did not name an heir, his will would be considered a codicil, and his bequests would become fideicommissa. This "opened a way to save certain dispositions in a will which was invalid due to some formal or substantive defect": if a testator failed or chose not to name an heir, an estate would go to heirs via rules of intestacy, but those heirs would be burdened by the fideicommissa in the codicil.

By the time of the Codex Justinianus, the formal requirements related to wills had relaxed, while requirements for the codicil had become more stringent. "There was thus little difference between the formalities for a will and for a codicil," and an invalid will – where, for example, no heir had been named – could often be upheld as a codicil.

It is acknowledged that classical Roman succession law was "highly complicated and to a large extent perplexedly entangled".

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