A codicil is a legal supplement to an existing last will and testament that amends, modifies, or adds specific provisions without revoking the entire original document. Under the Uniform Probate Code (UPC) Section 2-502 and corresponding state statutes, a codicil must meet the same execution requirements as a will itself -- meaning it must be signed by the testator and properly witnessed to be legally valid.

The codicil has been a recognized instrument in Anglo-American law for centuries, allowing testators to make targeted changes to their estate plans without the time and expense of drafting an entirely new will. When a codicil is probated, it is read together with the original will as a single integrated document. Any provisions in the codicil that conflict with the original will supersede the earlier terms, while all non-conflicting provisions of the original will remain in full effect.

It is important to note that a codicil effectively "republishes" the original will as of the codicil's date. Under UPC Section 2-509, this republication can have practical consequences -- for example, if a beneficiary named in the original will predeceased the testator but a new beneficiary is alive on the codicil date, the republication may resolve certain lapse issues. Estate planning attorneys generally recommend limiting codicils to minor changes; if extensive revisions are needed, drafting a new will with a revocation clause is typically more reliable and less likely to create ambiguity during probate.

A codicil is appropriate when you need to change the executor or alternate executor named in your will -- for instance, if your original executor has passed away, become incapacitated, moved out of state, or you simply prefer a different person for the role.

If you want to update a specific bequest -- such as leaving a piece of jewelry to a different family member or changing the dollar amount of a charitable gift -- a codicil allows the targeted change without disturbing the rest of your estate plan.

After a life event such as the birth of a grandchild, you may want to add a new beneficiary. A codicil can insert the new provision without requiring you to redistribute all other bequests. Similarly, if a named beneficiary passes away and you want to redirect their share, a codicil handles this efficiently.

Changing the guardian designated for minor children is another common reason. If your chosen guardian is no longer willing or suitable, a codicil names the replacement while keeping all other provisions intact.

However, a codicil is not recommended for substantial restructuring of your estate plan, changes to trusts established under your will, or situations where multiple prior codicils already exist. Multiple codicils attached to a single will can create confusion and increase the risk of probate challenges. In those cases, executing a completely new will is the safer approach.

The codicil must open with a declaration identifying the testator by full legal name, stating the date of the original will being amended, and confirming that the testator is of sound mind and acting voluntarily. This mirrors the testamentary capacity requirements under state probate codes.

A specific reference to each provision being amended is essential. Rather than restating the entire will, the codicil should identify the exact article, section, or paragraph number being changed and state the new language that replaces or supplements it. Vague references -- such as "I change my bequests" without specifying which ones -- invite probate challenges.

A ratification clause must confirm that all provisions of the original will not expressly modified by the codicil remain in full force and effect. This prevents any argument that the codicil impliedly revoked other portions of the will.

Witness requirements must match those of the original will. Most states require two disinterested witnesses (persons who are not beneficiaries) who observe the testator's signature and sign the codicil themselves. Under UPC Section 2-502, witnesses must be present at the same time in many jurisdictions. Louisiana uniquely requires notarized form for all testamentary instruments under its Civil Code.

A self-proving affidavit, signed before a notary public by the testator and witnesses, eliminates the need to locate witnesses during probate to authenticate the codicil. This is authorized under UPC Section 2-504 and adopted in the vast majority of states.

The codicil should be stored with the original will -- physically attached if possible -- to ensure both documents are found and presented to the probate court together. The testator should note the codicil's existence in any letter of instruction provided to the executor.