What Is a Codicil? How Will Amendments Work in Practice

What a codicil does — and does not do

A codicil amends specific provisions of an existing will. It might:

• Change the executor named in the will
• Add or remove a specific gift (a pecuniary or specific legacy)
• Change the beneficiary of a specific bequest
• Update the share of residue allocated to each beneficiary
• Add or change a guardian for minor children
• Revoke (cancel) a particular clause in the original will

A codicil does not replace the original will. The two documents must be read together. Any provision of the original will that is not addressed by the codicil continues in full force.

A codicil also differs from a new will, which typically contains a revocation clause that cancels all previous wills entirely. If the testator wanted to make sweeping changes, the better approach is usually to write a new will rather than amend piecemeal with a codicil.

Formal requirements for a valid codicil

Under the Wills Act 1837, a codicil must comply with the same formalities as a will:

1. In writing — it must be a physical document (or since September 2020, exceptionally, a video will, but this remains rare and untested in the courts).
2. Signed by the testator — the testator must sign (or acknowledge their signature) in the presence of two witnesses present at the same time.
3. Witnessed by two independent adults— both witnesses must be present when the testator signs and must sign the codicil themselves in the testator's presence. For the rules on valid witnessing, see our guide on will witnessing rules.
4. The testator must have testamentary capacity — they must understand what they are doing and the effect of the amendment.
5. No undue influence— the codicil must be the testator's free and voluntary act.

A codicil that fails any of these requirements is invalid. If you discover an invalid codicil, the original will stands unaffected as though the codicil had never existed — but you should take legal advice before proceeding.

Common uses for codicils

Changing executor

If the executor named in the will has died, lost mental capacity, or the testator simply wants a different person to act, a codicil can substitute a new executor. As the administering executor, check whether the codicil executor is still willing and able to act — they can renounce at any time before applying for probate.

Adding or changing specific gifts

The testator may have acquired new assets (a painting, a car, jewellery) after writing the original will, or may have changed their mind about who should receive a particular item. A codicil can add a new specific gift or replace an existing one. See our guide on pecuniary legacies for more on specific and cash gifts.

Updating residuary beneficiaries

A codicil might adjust the percentage shares of the residuary estate — for example, changing a 50:50 split between two children to 60:40 after a family change in circumstances. See our guide on what the residuary estate means to understand how this affects distribution.

Adding a life interest trust

A codicil can create a new life interest trust that was not in the original will, or amend the terms of an existing trust. Given the complexity of trust drafting, this should always be done by a solicitor — a poorly drafted codicil creating a trust can cause significant administration problems.

How a codicil affects the probate application

When you apply for probate using form PA1P, you must:

• List every codicil to the will (including the date of each codicil).
• Submit the original codicil(s) to the Probate Registry alongside the original will.
• Pay the standard probate application fee of £273 — you do not pay extra for codicils.

The Probate Registry will consider the will and all codicils together when issuing the Grant of Probate. The Grant will refer to the will "together with one [or more] codicil[s]". See our detailed guide on the PA1P probate application.

If you have lost the original codicil but have a photocopy, the Probate Registry may accept the copy in exceptional circumstances, but this requires a formal application and supporting affidavit evidence. Seek legal advice if the original codicil cannot be found.

Priority: codicil versus will

Where a codicil and the original will conflict, the codicil governs — provided it was executed later and is itself valid. The rule is simple: the most recent validly executed provision wins.

Non-conflicting provisions of the original will remain in force. In the example above, specific gifts to Alice, Ben, and Clara in the original will (if any) are unaffected unless the codicil specifically addresses them.

Validity problems to watch for

Unwitnessed codicils

A codicil without two witnesses is invalid. It has no legal effect, and the original will stands as though the codicil had never been written. Do not attempt to administer the estate according to an unwitnessed codicil.

Codicil witnessed by a beneficiary

If a codicil creates or confirms a benefit for someone who acted as a witness, the same rule as for wills applies under s.15 Wills Act 1837: the gift in the codicil fails but the codicil itself (and the original will) remains valid. See our guide on wills witnessed by a beneficiary for the full analysis of how this affects distribution.

Codicil that accidentally revokes more than intended

Poorly drafted codicils sometimes contain wide revocation language ("I revoke all previous wills and testamentary dispositions"). If the codicil contains such a clause, it may have revoked the original will entirely rather than just amending it. Read the codicil very carefully. If in doubt, take legal advice before applying for probate.

Capacity issues

If there are concerns that the testator lacked mental capacity when the codicil was made (for example, because they had dementia), the validity of the codicil can be challenged. This is a form of contentious probate — see our guide on what is contentious probate.

Codicil versus new will: which is better?

Codicils have largely fallen out of favour with solicitors. There are several reasons:

• Complexity risk: Multiple codicils over many years can make a will very difficult to interpret — it is easy to miss a provision or misunderstand the cumulative effect.
• Inconsistency: A codicil written without sight of the full will may create inconsistencies or unintended results.
• Loss of documents: The more separate documents that exist, the greater the risk that one cannot be found when the testator dies.
• Modern practice: Solicitors can now reprint and re-execute a complete new will at minimal cost, making a fresh will a cleaner and safer approach in most cases.

In some circumstances a codicil remains the practical choice — for example, where the testator is ill and execution formalities need to be kept as simple as possible, or where a court is authorising an amendment to a will (a statutory will) for a person lacking capacity.

For advice on writing a new will from scratch, see our guide on how to write a will in the UK.

Frequently asked questions