What does a codicil do?
A codicil adds to, changes or removes part of a will. The will and every codicil are read together as one set of instructions. GOV.UK describes a codicil as the only way to change a will after it has been signed, other than making a new will. Typical uses are replacing an executor, adding a small gift or updating a beneficiary's name.
Does a codicil need the same signing as a will?
Yes. A codicil must be in writing and signed in front of two witnesses present at the same time, who each then sign in your presence (Wills Act 1837, section 9). The same witness rules apply: a gift to a witness, or to a witness's spouse or civil partner, fails (section 15). The witnesses can be different people from those who witnessed the will. The steps are in how to sign and witness a will.
A handwritten note on the will itself is not a codicil. Changes written on a signed will have no effect unless they are signed and witnessed (section 21).
Codicil or new will: which should you use?
| Change | Usually better |
|---|---|
| Replacing one executor | Codicil or new will |
| Adding a single small gift | Codicil or new will |
| Changing shares of the residue | New will |
| Adding or removing main beneficiaries | New will |
| After marriage or civil partnership | New will: the old will is usually revoked, so there is nothing for a codicil to change |
| After divorce | New will |
See does marriage revoke a will and does divorce affect a will.
What problems can codicils cause?
- They can be separated from the will. Keep every codicil with the original will and tell your executors it exists.
- They can conflict. Each codicil is read with the will and every earlier codicil, so unclear wording in one can change the meaning of another.
- They need the full ceremony. A codicil takes the same effort to sign as a new will, so for more than a small change a new will is rarely more work.
How do you replace a will and its codicils?
Make a new will that says it revokes all previous wills and codicils, sign and witness it, then destroy the old documents, as GOV.UK suggests. Under section 20, a later will revokes an earlier one in this way. Changing your will covers the options, and SwiftWill customers can prepare a replacement for the same people without paying again under the terms.
Sources
- GOV.UK: Update your will
- Wills Act 1837: sections 9, 15, 20 and 21
Sources checked 24 September 2026.