A codicil is a short, separate legal document that changes one part of an existing will, for example a new executor, an updated address, or a small extra gift, without you having to rewrite the whole thing. It must be signed and witnessed exactly like a will, and once it’s signed it becomes legally part of the will it amends. Gov.uk’s own guidance on updating a will puts it simply: “If you want to update your will, you need to make an official alteration (called a codicil) or make a new will.” This guide covers what a codicil can and can’t do, how to make one properly, what it costs, and when a fresh will is the better choice.
What is a codicil, exactly
A codicil is a supplementary document, not a standalone will. It doesn’t replace your will; it sits alongside it and modifies specific clauses while leaving everything else in force. Because it’s legally treated as part of the will it amends, it carries the same legal weight, and it must pass the same formal tests to be valid. If any part of a codicil is unclear or improperly witnessed, that part can fail even if the rest of the will remains valid.
A codicil typically does one of a small number of things:
- Adds a new gift or removes an existing one
- Changes or adds an executor
- Updates a beneficiary’s name or address (people change surnames on marriage, move house, and so on)
- Corrects a factual error in the original will
It is not designed for a wholesale rewrite. If you’re changing who inherits the majority of your estate, or making several unrelated changes at once, a new will is the safer route (see “When to write a new will instead” below).
If what you want to change is informal, guidance on who should have a sentimental item, or funeral preferences, rather than a legally binding change, you may not need a codicil at all. A letter of wishes covers that kind of guidance without needing to be signed or witnessed.
The legal requirements for a valid codicil
A codicil in England, Wales, and Northern Ireland must meet the same signing and witnessing rules as a will, set out in section 9 of the Wills Act 1837:
| Requirement | What it means |
|---|---|
| In writing | Typed or handwritten, both are valid |
| Signed by the testator | Or by someone else in their presence, at their direction |
| Two witnesses | Both present together when you sign or acknowledge your signature |
| Witnesses sign too | Each witness signs in your presence, after you |
| Witnesses over 18 | Confirmed in gov.uk's guidance on making a will legal |
| No benefit to witnesses | A witness (or their spouse/civil partner) who is left anything in the codicil loses that gift |
Gov.uk’s guidance on making sure your will is legal states plainly: “You cannot leave your witnesses (or their married partners) anything in your will.” The same rule applies to a codicil. If you’re adding a new small gift to someone in a codicil, don’t ask that person, or their spouse, to witness it.
You do not need to use the same two witnesses who signed your original will. Any two independent adults will do, as long as they meet the requirements above and are both physically present when you sign.
What a codicil can and can’t fix
| Good use for a codicil | Better handled with a new will |
|---|---|
| Swapping one executor for another | Changing who inherits most of the estate |
| Adding a single small cash gift | Making several unrelated changes at once |
| Correcting a beneficiary's changed name or address | Restructuring gifts between multiple beneficiaries |
| Revoking one specific clause | You already have one or two codicils on the will |
The gov.uk guidance on writing a will does not set a hard rule on when a codicil stops being appropriate. The practical reasoning solicitors use is about clarity: every codicil is a document your executor has to read alongside the will, in the right order, to work out what actually happens to the estate. One codicil making one clear change is usually easy to interpret. Two or three, especially if a later codicil touches the same clause an earlier one already changed, start to create genuine risk of confusion or dispute between beneficiaries after you’ve died, when you’re no longer there to clarify what you meant.
Costs
A codicil is generally cheaper to prepare than a full new will, because it only needs to draft and formalise the specific change rather than the whole document. Costs vary by solicitor and by how much drafting the change actually needs, so ask for a fixed-fee quote before instructing anyone. A DIY codicil template is the lowest-cost route, but with no professional check against the rest of your will, it carries the highest risk that a wording slip invalidates the change or creates ambiguity your executor has to untangle later. If you already have a solicitor who drafted your original will, ask them for a like-for-like quote on a codicil against a fresh will – for anything beyond a single small change, the price gap is often smaller than people expect, and a new will removes the risk of the codicil and the original will disagreeing with each other.
How to make a codicil
- Write it clearly. State exactly which clause of the will you are changing, revoking, or adding to. Reference the original will by its date so there’s no ambiguity about which document it amends.
- Sign it. Sign the codicil yourself, in the presence of two witnesses, both present at the same time.
- Have your witnesses sign. Each witness signs in your presence, immediately after you.
- Store it with your will. Keep the codicil physically together with your original will, not in a separate file, drawer, or box. Tell your executor it exists and where to find it.
- Repeat for each change, but remember: multiple codicils increase the risk of confusion. If you’re on your third change, it’s usually time to consider a new will instead.
Codicils and probate
When your executor applies for probate after you die, gov.uk’s guidance on applying for probate where there’s a will is explicit that they need “the original will and any updates” – meaning every codicil, not just the will itself. A photocopy is not accepted for the will, and the same applies to codicils. Every codicil should be listed separately on the probate application form (PA1P) with its own date, so the probate registry can see the full, final set of terms.
This is the single biggest practical risk with codicils: if one goes missing, or your executor doesn’t know it exists, the estate could be administered under an out-of-date version of your will. Keeping every codicil physically attached to the original will removes this risk entirely.
What to avoid
- Don’t cross out or write on the original will directly. Unwitnessed handwritten alterations to a will are usually disregarded, and can raise doubt about the validity of the rest of the document. Always use a properly signed and witnessed codicil (or a new will) instead.
- Don’t let a witness or their spouse benefit from the codicil. The gift is void even though the rest of the codicil remains valid.
- Don’t stack codicils indefinitely. Each one adds a document your executor must locate, read, and reconcile with the will and every other codicil. At a certain point a new will, with a clause revoking all previous wills and codicils, is genuinely simpler for everyone who has to deal with your estate.
- Don’t store a codicil separately from the will. A codicil that isn’t with the will it amends may never be found.
Summary
A codicil lets you make a small, specific change to your will without rewriting the whole document, but it must be signed and witnessed exactly like a will under the Wills Act 1837, and both codicil and will must be sent together when your executor applies for probate. Use one for a single, isolated change. For anything more substantial, or once you’re stacking a second or third codicil, a fresh will drafted with the help of a solicitor found through the Law Society’s Find a Solicitor service is the clearer and safer route. See our guide on how to write a will for the full process, or how to find a will if you’re searching for a deceased relative’s documents.