What Is a Codicil and When Do You Need One?

A codicil is a formal written document that amends, modifies, or supplements an existing will without replacing it entirely. Think of it as an official amendment: the original will remains in effect, and the codicil changes only the specific provisions it addresses. If you need to update your executor, adjust a single bequest, or add a new beneficiary for a specific gift, a codicil can accomplish that without requiring you to rewrite your entire will.

The rule most people miss: a codicil is legally valid only if it meets the same formality requirements as the original will. An informal handwritten note or an unsigned typed page has no legal effect, no matter how clearly it states your intentions. Understanding this requirement — and knowing when a codicil is the right tool versus when a new will makes more sense — can save your estate significant confusion at probate.

What a Codicil Can Change

A codicil can make almost any change to a will that you could have made in the original document, including:

• Changing or replacing a named executor or alternate executor
• Updating a specific bequest — for example, directing a different item of personal property to a beneficiary, or increasing or decreasing a cash gift
• Adding a new beneficiary for a specific gift
• Removing a beneficiary from a specific bequest
• Updating the named guardian for minor children
• Adding or changing a charitable gift
• Clarifying language in the original will that has become ambiguous

A codicil does not revoke the entire will. It modifies only what it specifically addresses. Everything else in the original will remains exactly as written. When both documents are presented at probate, the court reads them together as a single integrated set of instructions — the original will plus the codicil's amendments.

What a Codicil Is Not Well-Suited For

A codicil works best for limited, targeted changes. It is not the right tool when:

• The changes are substantial. If you are significantly restructuring how your estate is divided, changing most of your beneficiaries, or altering the core logic of your estate plan, a new will produces a cleaner result than layering amendments onto the original.
• You already have one or more codicils. Multiple codicils stacked on top of each other can create a confusing document trail, especially when they interact in ways that are difficult to untangle. If there is any potential for contradiction between the original will and the codicils, or between two codicils, the risk of disputes increases.
• A major life event has changed your overall situation. Marriage, divorce, the birth of children, or the death of multiple named persons in your will are occasions to rethink the entire estate plan — not just patch individual provisions.

Formality Requirements: How to Execute a Valid Codicil

Because a codicil is legally part of your will, it must meet the same requirements your state imposes on wills in general. Those requirements vary by state but typically include:

• The codicil must be in writing
• You must sign it — you remain the testator
• The required number of witnesses — usually two — must observe you sign and then sign the codicil themselves
• Some states also require or strongly recommend notarization, particularly a self-proving affidavit that makes the codicil easier to admit to probate without calling witnesses to testify
• The codicil should clearly identify the will it modifies, typically by referencing the date the original will was signed

What does not work: a handwritten note stapled to your will, an unsigned typed page, an email or text message stating new instructions, or any document that omits the required witnesses. These informal changes have no legal effect in the vast majority of states — and they can muddy the waters at probate by suggesting the will is incomplete or that the testator tried to modify it outside the proper process.

One practical note: in states that recognize holographic wills — wills written entirely in the testator's own handwriting without witnesses — a holographic codicil written entirely by hand and signed may also be valid. But holographic instruments are not recognized in every state, and they carry their own risks. Do not assume this applies in your state.

Codicil vs. New Will: Which Is the Right Choice?

Both are legally valid ways to update your testamentary wishes. The practical question is which produces the clearest and most reliable result.

• Use a codicil when the change is minor and clearly defined, the original will is otherwise accurate and current, and you have not already accumulated prior codicils.
• Use a new will when the changes are substantial, when you already have one or more prior codicils, when your overall circumstances have changed significantly since the original was drafted, or when simplicity and clarity are the priority.

A new will with a clear revocation clause — language expressly revoking all prior wills and codicils — produces a single, self-contained document that eliminates any ambiguity about which version controls. Many estate planning attorneys prefer executing new wills over codicils for this reason: a single, clean document is easier to probate and harder to challenge than a will plus one or more amendments.

What Happens at Probate?

When you die, your executor files both the original will and any valid codicils with the probate court. The court reads them together. In the event of a direct conflict between a provision in the original will and a provision in a codicil, the codicil generally controls — it is the more recent expression of your intent. But conflicts and ambiguities can lead to delays, attorney fees, and challenges from disappointed heirs. The cleaner your documents, the smoother probate tends to go.

What You Can Do

• Define the scope of the change before drafting anything. A codicil works best when the change is specific and limited. Write down exactly which provision you want to amend and what you want it to say.
• Meet your state's formality requirements. Do not sign a codicil without the required witnesses present. Check your state's current probate code — requirements vary.
• Consider whether a new will is the cleaner solution. If you find yourself writing a lengthy codicil, or if this would be your second or third codicil, a fresh will with a revocation clause is almost certainly the better path.
• Keep the codicil with the original will. Store the signed codicil together with your original will. If an attorney holds the original, provide the signed codicil so their records are complete and consistent.
• Destroy prior documents when you execute a new will. If you later decide to make a new will that revokes all prior documents, destroy the codicils along with the old will to prevent any possibility of confusion.
• Update beneficiary designations separately. A codicil cannot change the beneficiary on a life insurance policy or retirement account. Those must be updated directly with the institution that holds the account.

This article is general legal information, not legal advice. Will and codicil requirements are set by state law and vary significantly from state to state. Check your state's probate code or consult a licensed estate planning attorney in your state before drafting or executing a codicil.