A codicil is a document that changes or adds to an existing will without replacing the whole instrument. It can sound like an easy answer when only one detail needs updating. Whether it is the best answer depends on the change and the state of the existing will.
Both documents must work together. If their wording is inconsistent, or if there are several codicils, the executor may have to untangle a sequence of amendments instead of following one clear set of instructions.
When a codicil may be suitable
A carefully drafted codicil may be appropriate for a limited change, such as replacing an executor, where the rest of the will remains suitable. It should identify the will accurately and state precisely what is being changed.
It still needs proper signing and witnessing. Calling a note a codicil does not make an informal handwritten instruction legally effective. Nor should you assume that changing a digital copy alters the signed document held in storage.
When a fresh will is clearer
A new will is often preferable when beneficiaries, family circumstances or several gifts have changed. It provides an opportunity to check the entire plan, including the residue and substitute arrangements.
Consider a person who wants to remove one cash gift, add another beneficiary and change the executor. Each individual amendment might seem small, but together they can affect the balance and interpretation of the document. A complete review may be simpler than layering new wording over old.
Check what remains in force
A codicil can have effects beyond the sentence being changed, including consequences for the relationship between earlier documents. If there is doubt about whether a will has been revoked, or if there are foreign wills, obtain advice before signing anything.
Keep the operative documents together and tell the executor where the originals are stored. Avoid leaving an earlier will and an unexplained series of copies that appear equally current.
Before choosing a format, describe the intended change in plain language and read the existing will from beginning to end. If the document no longer fits your circumstances, a short amendment may only postpone the more useful task: preparing a coherent replacement that reflects your wishes as they stand now.
Sources and further reading
General information, not advice on your individual circumstances. Laws and tax rules can change; check the linked official guidance and obtain professional advice where needed.