Codicil to a Will in Australia: How to Change Your Will

You have a will sitting in a drawer somewhere, and something in it is no longer accurate. Maybe the executor you named has moved overseas. A grandchild has arrived. You’ve sold the house the will talks about.

You don’t want to start again from scratch. You want to fix that one part.

The short answer to doing this is a codicil, which is a short legal document that changes part of an existing will without rewriting the whole thing. Under section 3 of the Succession Act 2006 (NSW), the definition of a “will” includes a codicil, so a codicil has to be signed and witnessed the same way your will was. Same care, smaller document.

Two questions decide what you do next. Is a codicil the right tool for your change, or do you need a new will? And how do you make the change so it holds when your estate is being administered and you’re not there to explain it?

This page works through both. I’m writing about New South Wales here, and every state and territory has its own equivalent Act, so check the rules where you live before you sign anything.

What a codicil actually is

A codicil is an add-on to your existing will. It names the will it changes, sets out the change, and leaves everything else in the will standing. You’ll also see it written as a codicil of will, or a codicil to a last will and testament. Same document, different labels.

The important part is what it isn’t. It’s not a note, a letter of instruction, or a memo to your executor. Legally it’s part of your will. The Act’s definition of a will includes a codicil, so the two documents are read together as one set of instructions, and when the time comes they’re usually produced together for probate.

That’s why a codicil isn’t a shortcut around the formalities. It’s a smaller document held to the same standard.

Three terms come up throughout, so here they are put simply. The testator is the person whose will it is, which here is you. The executor is the person who carries out the will after you die. A beneficiary is anyone who receives something under it.

Codicil or a new will?

This is the decision most people skip, and it’s the one that matters.

Here’s the rule of thumb I use. A codicil suits one or two simple, self-contained changes. Swapping an executor. Adding a small gift. Changing the guardian you nominated for your children. A new will is the better move once the changes are numerous, once they interact with each other, or once something significant has changed in your life.

Most people over-use codicils. They make a change, then another, then another, and end up with a will and three add-ons that have to be read as one document by someone who wasn’t in the room for any of it. Stacked codicils get confusing, and confusion is where disputes start. The cost of a fresh will is usually less than the cost of arguing about which document says what.

People also change their minds, and that’s worth being honest about. It’s a common pattern in estate practice: someone takes a person out of their will, and within a few months wants them back in. If your thinking is still moving, don’t paper over it with a series of amendments. Sit with the decision, then make a new will that says what you actually mean.

One more trigger for a new will rather than a codicil: marriage, divorce or a new child. Marriage and divorce change your will by operation of law. A new child doesn’t, which is exactly why you have to make the change yourself. I’ve set out how the first two work further down.

How to make a codicil that holds up

There’s no prescribed court form for a codicil. What there is, under section 6 of the Succession Act 2006 (NSW), is a set of execution requirements you have to meet. Section 6 sets three:

1. Put it in writing. Verbal instructions to a family member change nothing.
2. Sign it yourself, in the presence of two or more witnesses who are present at the same time.
3. Have at least two of those witnesses sign the codicil.

Those three decide whether the codicil is validly executed. On top of that, three things stop a valid codicil causing trouble later. They aren’t in the Act, they’re just what keeps a document out of an argument:

1. Name the will you’re changing by its date, so there’s no doubt which document the codicil attaches to.
2. State the change clearly. Say which clause you’re altering and what it now says, and confirm the rest of the will stands.
3. Date it and store it with the will, so the two are found together.

Now the part people get wrong. Here’s the catch: your witnesses shouldn’t be beneficiaries. Under section 10, a gift to a person who witnesses the document can be void, which means you’ve quietly disinherited the person you were trying to look after. The codicil itself doesn’t automatically fail; the gift is what’s at risk. The spouse of a beneficiary isn’t caught by that section in New South Wales, but don’t use them either, because it invites an argument nobody needs. Use two independent adults who take nothing under the will.

Who can make a codicil

The same three conditions that apply to making a will apply here.

You need to be 18 or over. Narrow exceptions exist, but as a general rule that’s the line.

You need to be of sound mind when you sign, which means understanding what you’re changing and what effect the change will have.

And it has to be your own decision, made freely. If someone stands to gain and they’re the one arranging the appointment, driving you to it, and telling you what to say, that’s the pattern a court looks at later when a codicil is challenged.

What a codicil costs

Cost is usually the reason people are weighing a DIY kit against a solicitor, so here are real numbers rather than “it depends”.

The typical market range for a solicitor-drafted codicil is $350 to $500. A DIY kit or online template typically sits at $39 to $50.

So the kit is cheaper. The honest way to look at the difference is what each one buys you. The template gives you a document. The solicitor gives you a document plus a check that the change does what you think it does, is executed properly, and doesn’t collide with the rest of the will.

That check is where the value sits, because the failure mode is expensive. A codicil that’s badly executed or badly worded isn’t discovered by you. It’s discovered by your executor and your family after you die, and fixing it then means a court application, legal costs on both sides, and a delay in your estate being distributed. A few hundred dollars saved at the front can cost tens of thousands at the back.

Where a codicil earns its keep is the simple, clean change: one clause, no flow-on effects. Where it doesn’t is anything you’re not sure about.

Can you just cross out or handwrite a change on your will?

No. This is the single most common DIY mistake, so here’s why it fails.

An alteration made to a will after it’s been signed isn’t effective unless it’s executed the same way a will is, which means signed and witnessed (section 14, Succession Act 2006 (NSW)). Crossing out a name, writing a new figure in the margin, or initialling a change usually does nothing. The original wording generally stands, and your handwriting simply raises a question about what you intended.

There is a limited safety net. Under section 8, the dispensing power, a court can accept a document that doesn’t meet the formal requirements if it’s satisfied the person intended it to form their will or an alteration to it. Courts have accepted marked-up documents this way.

Don’t read that as permission. Section 8 is a rescue, not a plan. It means somebody has to make an application to the Supreme Court, pay for it out of the estate, and persuade a judge about what you meant, with you unavailable to confirm it. It also gives anyone unhappy with the change a clear opening to dispute it.

The takeaway is simple. Leave the original will alone. If you want to change something, make a proper codicil or a new will.

How marriage, divorce and separation affect your will

This is where a lot of people get caught out, because these events change your will whether or not you touch it.

Marriage. Getting married generally revokes your existing will, unless the will was made in contemplation of that marriage (section 12). A gift to the person you actually marry, and their appointment as executor, survive the revocation. The rest doesn’t. If you married after making your will and nobody raised this with you, most of what you wrote may no longer stand, which means the law, not your will, would decide who receives what.

Divorce. A divorce or an annulment doesn’t cancel your whole will. It revokes any gift to your former spouse and their appointment as executor, treating them as though they had died before you (section 13). That can leave a gap in your will where a substantial gift used to be, and no one holding the role of executor. Know what an executor does before you assume the next person on your list will simply step in.

Separation. Separating changes nothing. Your will stands exactly as written, and if your ex is still named in it, your ex still takes under it. Plenty of people separate, move on with their lives, and never update the document that decides where everything goes.

After any of these three, a codicil is usually not the answer. Review the whole will.

Common mistakes with codicils

• Stacking codicils. Several add-ons made over the years start to contradict each other. Once you’re on your second or third, make a new will.
• Using a beneficiary as a witness. The gift to that person can be void under section 10. Their spouse isn’t caught by the section, but using them still invites an argument.
• Storing the codicil away from the will. The two are read together, and they usually need to be produced together for probate. A codicil nobody finds is a codicil that never happened.
• A sloppy revocation clause. Wording that revokes more of the will than you intended can wipe out clauses you meant to keep. This is the clause to get a solicitor across.
• Not dating it. Where documents conflict, the dates decide which came last.
• Changing something the will cannot control. Superannuation with a valid binding nomination and jointly held property often pass outside your estate, so a codicil doesn’t redirect them.

Can a codicil be challenged?

Yes, on the same grounds as a will:

• The person lacked capacity when they signed it.
• They were pressured or unduly influenced into making it.
• It wasn’t executed properly.
• It’s a fraud or a forgery.

A codicil can also be caught by a family provision claim, where someone eligible argues the estate didn’t make adequate provision for them. That’s a different argument from attacking the document itself, and the difference matters if you’re thinking about how someone might challenge a will.

One thing that reassures people: a will or codicil is only revoked in the ways the Act allows (section 11). Someone can’t simply decide your codicil doesn’t count. If they want it set aside, they have to make a case.

If you know a change is going to upset someone, that’s an argument for having a solicitor draft it and keep a file note, not an argument for doing it quietly at the kitchen table. Good records at the time are what defends the document later. The Law Society of NSW wills and estates guidance is a useful plain-English starting point if you want to read further before you call anyone.

Where to from here

If your change is small and self-contained, a codicil will do the job, provided it’s signed and witnessed properly and stored with the will. If you’ve had a life event, or you’re on your second or third change, make a new will instead.

If you’re not sure which side of that line you’re on, that’s a short conversation, not a big engagement. Book a free discovery call with our team, tell us what you want to change, and we’ll tell you straight whether it’s a codicil job or a new-will job. Call 1300 614 732, or read more about how we help on our wills and estates lawyers page.