Most worries about an invalid will are about the wrong thing

Two quite different questions get asked in the same words. One is whether the will is valid, which is about how it was made and whether anything has since revoked it. The other is whether someone left out of it can do something about that, which is a family provision claim and has nothing to do with validity at all. A will can be perfectly valid and still be challenged successfully by a person the testator did not provide for.

This article is about the first question only. It sets out what actually makes a will invalid in New South Wales and the Australian Capital Territory, and what quietly revokes one that was valid when it was signed.

The two jurisdictions look similar and are not. On one point that comes up constantly, a gift to a witness, they produce opposite results on identical facts.

Execution: what the two Acts actually require

The formal requirements are short, and almost every homemade will that fails, fails on one of them.

Two of those differences matter in practice.

Whether the witnesses have to sign in front of each other. New South Wales says expressly that they do not. The ACT provision requires each witness to subscribe in the presence of the testator and of the other witness or witnesses. A will signed by two witnesses who came in one after the other satisfies section 6 in New South Wales and is a problem under section 9 in the ACT.

Where the signature goes. Section 6(2) in New South Wales says the signature must be made with the intention of executing the will and that it is not essential for it to be at the foot. The ACT provision says "at the foot or end", but section 10(1) softens it: the position of the signature does not invalidate the will if it is apparent on the face of the will that the testator intended to give effect by that signature to the writing signed as their will.

One thing that does not matter in either jurisdiction is whether the witnesses knew what they were signing. Section 7 in New South Wales says so expressly, and section 14 in the ACT provides that a will is not voided by the incompetence of a witness.

A document that fails the formalities can still be a will

Both jurisdictions have a dispensing power, and it is wider than most people expect. It is the reason a note, a draft, an unsent letter or a document on a phone can end up admitted to probate.

Section 8 of the Succession Act 2006 (NSW) applies to a document, or part of a document, that purports to state the testamentary intentions of a deceased person and has not been executed in accordance with the Act. That document forms the will, or an alteration to it, or a full or partial revocation of it, if the Court is satisfied that the person intended it to. Section 11A of the Wills Act 1968 (ACT) is to the same effect.

What the Court may look at is the significant part. Under section 8(3) it may have regard, in addition to the document itself, to any evidence relating to the manner in which the document was executed and to any evidence of the testamentary intentions of the deceased, including evidence of statements made by them. Section 8(4) makes clear that this does not limit what else may be considered. The ACT provision carries the same two heads.

A gift to a witness: the two jurisdictions go opposite ways

This is the single most useful thing to know if you act, or advise, across the border.

In New South Wales, section 10 provides that where a beneficial disposition is given by will to a person who attests the execution of the will, the disposition is void to the extent that it concerns that interested witness or anyone claiming under them. The gift fails; the will does not.

Section 10(3) saves the gift in three situations:

• at least two of the people who attested are not interested witnesses; or
• everyone who would benefit directly from the avoidance consents in writing to the distribution under the will, and has capacity to consent; or
• the Court is satisfied the testator knew and approved of the disposition and that it was given freely and voluntarily.

Section 10(4) confines what counts as a beneficial disposition: it does not include a charge or direction to pay a debt, or reasonable remuneration to an executor, administrator or legal practitioner acting in the administration.

In the ACT, section 15 of the Wills Act 1968 says the opposite in one sentence. No will or testamentary provision is void by reason only that the will was attested by a person, or the domestic partner of a person, who has or may acquire an interest under it. Sections 18 and 19 add that a creditor and an executor are each admitted as a witness.

None of which is a reason to have a beneficiary witness a will anywhere. It is a reason to check which side of the border the will was signed on before advising that a gift has failed.

Age, and the exceptions nobody remembers

A will made by a minor is not valid, and both Acts then carve out the same handful of cases. Section 5(1) of the Succession Act says a will made by a minor is not valid. Section 8(1) of the Wills Act 1968 says the same of a child.

The exceptions in New South Wales, in section 5(2), are a will made in contemplation of marriage, which is of no effect if the contemplated marriage does not take place; a minor who is married; and a minor who has been married revoking a will made while married or in contemplation of that marriage. Section 5(3) preserves a court-authorised will under section 16.

The ACT is the same in structure and wider in its trigger, because section 8 extends to a civil union as well as a marriage: a child who is or has been married or in a civil union may make or revoke a will, and a will made in contemplation of a marriage or civil union becomes valid on solemnisation or entry.

Capacity, which neither Act defines

Testamentary capacity is the ground most wills are actually challenged on, and it is not in either statute. Neither the Succession Act 2006 (NSW) nor the Wills Act 1968 (ACT) sets out a test. Both legislate around the concept: each has provisions allowing the Supreme Court to authorise a will for a person who lacks testamentary capacity, which presuppose the concept without defining it.

Capacity is governed by the general law, and the test is not set out in this article. That is deliberate: it comes from case law, the authorities on it were not read for this piece, and a half-remembered statement of a four-limb test is exactly the kind of thing that should not be published. If capacity is in issue, it is a question for advice on the medical and factual evidence rather than something to be resolved from an article.

What is worth saying is when it becomes an issue. Capacity is assessed at the time the will was made, not later. A diagnosis does not decide it and neither does age. What decides it is contemporaneous evidence, which is why a will prepared while capacity is deteriorating should be made with a file note, a medical opinion taken at the time, and a record of the instructions. Those are cheap to create then and impossible to create afterwards.

What revokes a will without anyone intending it

Two life events revoke a will or part of it by operation of law, and this catches more valid wills than any defect in execution.

Marriage

In New South Wales, section 12(1) provides that a will is revoked by the marriage of the testator. Section 12(2) preserves a disposition to the person the testator is married to at death, an appointment of that person as executor, trustee, advisory trustee or guardian, and a will exercising certain powers of appointment. Section 12(3) is the important escape: a will made in contemplation of a particular marriage is not revoked by that marriage, whether or not the contemplation is expressed in the will.

In the ACT, section 20(1) extends the trigger to a civil union or civil partnership as well as marriage, and narrows the escape: the will survives only where it was expressed to have been made in contemplation of that marriage, civil union or civil partnership. A New South Wales will that relies on unexpressed contemplation would not be saved by the ACT provision.

Divorce or termination

Section 13(1) of the Succession Act provides that divorce or annulment revokes a beneficial disposition to the former spouse, an appointment of them as executor, trustee, advisory trustee or guardian, and a grant of a power of appointment exercisable by or in favour of them. Section 13(2) makes that subject to a contrary intention appearing in the will, and section 13(3) preserves their appointment as trustee of property left on trust for beneficiaries including their children, and a power of appointment exercisable exclusively in favour of the children of both.

Section 20A of the Wills Act 1968 does the equivalent in the ACT on the termination of a marriage, civil union or civil partnership.

How a will is deliberately revoked

The list is closed, and it is shorter in the ACT.

Section 11(1) of the Succession Act 2006 (NSW) provides that the whole or part of a will may be revoked only: by an order under section 16 or 18; by the operation of section 12 or 13; by a later will; by writing declaring an intention to revoke, executed in the manner a will must be executed; by the testator, or someone in their presence and at their direction, burning, tearing or otherwise destroying the will with the intention of revoking it; or by writing on or dealing with the will in such a way that the Court is satisfied from the state of the will that the testator intended to revoke it.

Section 11(2) closes off the argument people most often try: no will may be revoked by any presumption of an intention on the ground of an alteration in circumstances. A change in the family, in the assets or in the relationship revokes nothing.

Section 21 of the Wills Act 1968 (ACT) is to similar effect but has no equivalent of the sixth New South Wales limb. In the ACT, revocation is by a subsequent valid will, a document executed like a will showing an intention to revoke, or destruction with that intention. There is no "state of the will" route.

The will the Court makes

Where a person has lost capacity, a will can still be made for them, but only by the Supreme Court and only on a strict test.

In New South Wales, section 18(1) allows the Court, on application by any person, to authorise a will to be made or altered in specific terms it approves, or revoked, on behalf of a person who lacks testamentary capacity. Leave is required under section 19, and section 18(3) requires the person to be alive when the order is made. Section 18(4) extends it to a minor who lacks capacity.

In the ACT, section 16A does the equivalent, and section 16E sets out what the Court must be satisfied of before granting leave: that there is reason to believe the person is, or is reasonably likely to be, incapable of making a will; that the proposed will is, or is reasonably likely to be, one that would have been made by the person if they had capacity; that it is or may be appropriate; that the applicant is an appropriate person; and that adequate steps have been taken to allow representation of everyone with a legitimate interest, including anyone with reason to expect a gift.

The second of those is the substance of the exercise. The Court is not deciding what would be fair. It is reconstructing what this person would have done.

Where this article stops

The position stated is as at 27 August 2026, read on that date from the Succession Act 2006 (NSW) in force consolidation and from republication 22 of the Wills Act 1968 (ACT), effective 23 February 2026.

There is more than one route, and they run on different clocks

The first mistake in a defect claim is assuming there is one cause of action and one time limit. In New South Wales there are at least three routes to a remedy against the people who built a defective building, and each has its own requirements, its own defendants and its own deadline. In the ACT the structure is similar but the questions are not the same, and an answer carried across from one jurisdiction to the other is often wrong.

The third of those is the one that changed the landscape, and it is dealt with below at some length because it is both the widest route and the least understood.

The statutory warranties in New South Wales

Section 18B of the Home Building Act 1989 (NSW) implies six warranties into every contract to do residential building work. They are implied by force of the section, so they do not depend on the contract saying anything, and they bind the holder of a contractor licence or a person who was required to hold one.

Section 18B(2) is the part that surprises people. The warranties are not limited to a contract with the owner of the land. They are also implied in the contract between a principal contractor who has contracted to do residential building work and a subcontractor engaged to do that work or part of it. The warranties run down the chain, which is why a head contractor facing a defect claim has a route against the trade that did the work.

The New South Wales clock: six years and two years, from completion

Section 18E is short and it decides most claims. Proceedings for breach of a statutory warranty must be commenced before the end of the warranty period, and the warranty period is:

• six years for a breach that results in a major defect in residential building work; and
• two years in any other case.

Both run from completion of the work to which the warranty relates. Where the work was not completed, section 18E(1)(d) fixes the start as the date the contract was terminated, or if it was not terminated, the date work ceased, or if work never started, the date of the contract.

There is one extension and it is easy to miss. Under section 18E(1)(e), where the breach becomes apparent within the last six months of the warranty period, proceedings may be commenced within a further six months after the period ends. A breach becomes apparent when a person entitled to the benefit of the warranty first becomes aware, or ought reasonably to have become aware, of it.

Section 18E(1A) provides a separate extension for strata work. Where a building bond has been lodged under Part 11 of the Strata Schemes Management Act 2015 (NSW), the two-year period is extended until 90 days after the end of the period for the final inspection report on the work.

The ACT splits the same period on a different question

The ACT also has six years and two years, and it divides them on a different test, so the same defect can fall in a different bucket on either side of the border.

Section 88 of the Building Act 2004 (ACT) implies warranties by force of the section into every contract for the sale of a residential building and every contract to carry out residential building work to which the builder is a party: that the work has been or will be carried out in accordance with the Act; in a proper and skilful way and in accordance with the approved plans; using good and proper materials; with reasonable promptness where no completion date is stated; and fit for a purpose or result made known so as to show reliance.

Two features of the ACT provision are worth noting. Section 88(3) provides that each of the owner's successors in title succeeds to the rights, so a purchaser inherits the warranty. And section 88(2A), inserted with the Property Developers Act 2024 (ACT), adds a warranty by the property developer where the developer arranged the work, additional to and not limiting the builder's warranty. That gives an owner a second solvent defendant in the case where it matters most, which is where the builder has gone.

Section 88(4) says the warranties end at the end of the period prescribed by regulation. The Act does not state the period. Section 38 of the Building (General) Regulation 2008 (ACT) does:

The ACT regulation defines a structural element as a load-bearing component of the building, internal or external, that is essential to the stability of the building or part of it, or a component including weatherproofing forming part of the external walls or roof. A non-structural element is anything else.

That definition does real work. A failure of external weatherproofing is a structural element in the ACT by definition, and therefore on the six-year clock, whatever view anyone takes of how serious it is. In New South Wales the same failure has to be argued as a major defect to get the six years.

The New South Wales statutory duty of care, and why it is the wider route

Part 4 of the Design and Building Practitioners Act 2020 (NSW) created a duty that is not confined to residential work and does not depend on any contract. Section 37(1) provides that a person who carries out construction work has a duty to exercise reasonable care to avoid economic loss caused by defects in or related to the building for which the work is done and arising from the construction work.

Four features make it the route to consider first in New South Wales.

Two further provisions close the obvious escapes. Section 39 provides that the duty cannot be delegated. Section 40 provides that Part 4 applies despite any contract to the contrary made after its commencement, and that no contract can annul, vary or exclude a provision of it: there is no contracting out.

Section 41 confirms the relationship with everything else. Part 4 is in addition to the duties, statutory warranties and other obligations under the Home Building Act, other Acts and the common law, and does not limit them. It is a route alongside the warranties, not a replacement for them.

For owners corporations there is a specific provision. Section 38 provides that an owners corporation is taken to suffer economic loss where it bears the cost of rectifying defects, including damage caused by defects, and that the loss includes the reasonable costs of providing alternative accommodation where necessary. It applies whether or not the owners corporation owned the land when the work was done.

Ten years, and then nothing

Both jurisdictions stop everything at ten years, and the longstop does not care when the defect was discovered.

In New South Wales, section 6.20 of the Environmental Planning and Assessment Act 1979 provides that a civil action for loss or damage arising out of or in connection with defective building work or defective subdivision work cannot be brought more than ten years after the date of completion. Completion is the date an occupation certificate is issued authorising occupation, or where no certificate is required, a compliance certificate; failing that, the date of a required final inspection by a certifier; failing that, the date the building was first occupied or used.

In the ACT, section 142 of the Building Act 2004 provides that a building action may not be brought more than ten years after the day a certifier gave the certificate of completion; or where there is none, the day of the last inspection in the course or on completion of the work; or where there is neither, the day the building was first occupied or used. Section 142(3) preserves any shorter limitation period under another territory law, so the ten years is a ceiling and not an entitlement.

The practical point is that the ten-year longstop and the warranty periods are different things doing different jobs. The warranty period can expire long before the longstop, and expiry of the warranty period ends that route whether or not ten years have passed.

In the ACT, each defendant pays only its share

Section 141 of the Building Act 2004 (ACT) applies proportionate liability to a building action. A defendant found liable is liable only for the amount of damages the court considers just having regard to the extent of that defendant's responsibility for the loss, and that liability is limited to the amount for which judgment is given against it even if another Act or rule of law provides otherwise. A defendant held liable for a proportionate part does not contribute to the damages apportioned to anyone else, and does not indemnify them.

The consequence for a plaintiff is that suing the most solvent defendant and leaving it to sort out contribution does not work. If responsibility is shared between a builder, a certifier and a designer, and two of them are gone, the one that remains pays its share and no more. So the identification of every potentially responsible party, and their solvency, is part of the assessment at the start of the matter rather than a detail for later.

What to do when a defect appears

The sequence matters more than the speed.

1. Fix the date of completion. Every clock in this article runs from it, and it is a documented date: the occupation certificate, the certificate of completion, the final inspection, or first occupation. Find it before doing anything else, because it tells you how much time you have and therefore how much deliberation you can afford.
2. Get the defect inspected and recorded. By someone whose report could be used later. Photographs with dates, and an opinion on cause rather than only on appearance, since the cause is what determines who is responsible.
3. Identify everyone who might be liable, not just the builder. In New South Wales the duty of care reaches designers, product suppliers, project managers and anyone with substantive control. In the ACT proportionate liability makes this decisive rather than merely useful.
4. Consider rectification by the original builder. It is frequently the cheapest outcome for an owner, and under a contract's own defects regime it may be a step that has to be offered.
5. Then choose the forum. Tribunal, court, or the contract's own dispute procedure. They differ on cost, speed and whether legal costs are recoverable, and the choice should follow the value of the claim rather than the seriousness of the defect.

Where this article stops

The position stated is as at 27 August 2026, read on that date from the official registers.