What Is a Codicil to a Will?

A codicil to a will is a short, formal legal document that makes a specific amendment to an existing will without replacing the whole document, such as changing an executor, adding a small gift, or updating an address. It must be signed and witnessed in exactly the same way as a will itself, and it only works well for one or two small, clear changes rather than a wholesale rewrite.

Written by Simon Jenkins, Curtis Legal LLP (Firm SRA No. 450129, Simon Jenkins SRA No. 167489). Call us on 0800 214 216 for a same-day callback.

What exactly does a codicil do?

A codicil sits alongside the original will as a separate document, legally read together with it, and it is used to vary, add to, or revoke a specific clause without disturbing the rest of the will. Typical uses include updating the name of an executor who has since died or become unable to act, adjusting a cash legacy to reflect inflation or changed circumstances, adding a newly acquired item or asset as a specific gift, or correcting a factual error such as a misspelled name or outdated address. Because it only touches the clauses it specifically mentions, everything else in the original will remains valid and unaffected.

When a codicil is appropriate, and when it is not

A codicil is a sensible, low-cost option when you need to make one or two minor, unambiguous changes to an otherwise still-accurate will. It becomes the wrong tool, however, once the changes start to multiply or interact with one another, and in several common situations a new will is clearly the better, safer choice:

Multiple changes

Each codicil is itself a legal document that must be read correctly alongside the original will and any earlier codicils. Once you have two or three codicils stacked on top of a will, the risk of inconsistency, contradiction, or simple confusion for your executors rises sharply. At that point it is almost always cheaper and safer in the long run to consolidate everything into a brand new will.

Marriage or divorce

Marriage automatically revokes an existing will in England and Wales unless the will was expressly made in contemplation of that marriage, and divorce (or the dissolution of a civil partnership) automatically cancels any gift to, or appointment of, the former spouse as executor, even though the rest of the will remains valid. The government guidance on making a will confirms this point clearly. A codicil cannot safely patch over the gap left by a marriage that has revoked the whole will; in that situation a new will is the only proper fix.

Significant life changes

The birth of children or grandchildren, a change in financial circumstances, selling or buying property, or a serious falling-out with a beneficiary are all situations where it is worth asking whether one small codicil really captures everything that needs to change, or whether it is a sign the will as a whole needs revisiting.

Formal requirements for a valid codicil

A codicil has no reduced formality compared with a will itself. To be valid it must:

• Be in writing and clearly identify the will it amends, usually by date and testator’s name.
• Be signed by the person making it (the testator) with the clear intention that it take legal effect.
• Be signed in the presence of two independent witnesses, who are both present at the same time and who then also sign the document themselves.
• Have witnesses who are not beneficiaries under the will or codicil, or married to a beneficiary, since this can void their gift under the will.
• Be made by someone who has the mental capacity to understand the change they are making, in the same way as making a will.

Missing any one of these formalities can render the codicil invalid, in which case the original will stands as though the codicil had never been written, often undoing the testator’s intentions entirely without them ever knowing.

Common mistakes with DIY codicils

Home-made codicil templates, bought online or copied from a generic form, cause a disproportionate number of problems during probate. Common issues include failing to identify the original will precisely enough, using language that is ambiguous about whether a clause is being replaced or merely supplemented, overlooking the witnessing rules, or using a beneficiary as a witness without realising the consequences. Because a codicil is read together with the will it amends, badly drafted wording can also create an unintended conflict between the two documents, which executors and, in the worst cases, the Probate Registry or the courts then have to resolve, sometimes at the estate’s expense. Knowing how to store a will safely matters here too, since a codicil that becomes separated from the will it amends, or is accidentally destroyed, can be just as damaging as one that was never validly made in the first place.

The cost of doing it properly

A solicitor-drafted codicil for a single, straightforward change is usually a modest fixed fee, considerably less than the cost of drafting a full new will, and it comes with the reassurance that the wording, formalities, and witnessing have all been checked by someone familiar with succession law. Given how much is at stake if a codicil turns out to be invalid or contradictory, and that a new will is often not much more expensive once more than one change is needed, it is worth taking advice before deciding which route is right for your circumstances.