The will does not do what someone expected it to do. Two different arguments follow.

Which of the two is in play changes everything that follows — the section relied on, the evidence gathered, and how long there is to act. It turns on the relationship to the person who died, how the will was signed, and when the death was.

Challenging whether the will is valid

This asks the Supreme Court of New South Wales not to admit the document to probate, or to revoke a grant already made. The grounds usually raised are:

• Lack of testamentary capacity — that when the will was made the person did not understand they were making a will, what they owned, or who might expect to benefit;
• Undue influence — that the will records someone else's wishes because the will-maker's freedom of choice was overborne. Persuasion is not enough;
• Failure of the formal requirements — section 6 of the Succession Act 2006 (NSW) requires a will to be in writing and signed, with the signature made or acknowledged before two or more witnesses present at the same time, at least two of whom must attest and sign it;
• Lack of knowledge and approval — that the will-maker did not know and approve of what they signed.

Where the will is valid but leaves someone out

Circumstances change; wills often do not. Where the will-maker simply never updated the document, the answer is usually a family provision claim under Chapter 3 of the Succession Act 2006 (NSW), not a validity challenge.

The Court may order provision out of the estate for an eligible person where adequate provision for their proper maintenance, education or advancement in life has not been made. Section 57 lists who is eligible: a spouse at the date of death; a de facto partner at that date; a child; a former spouse; a grandchild or member of the deceased's household who was at some time wholly or partly dependent on the deceased; and a person then in a close personal relationship with the deceased. For the last three the Court must also be satisfied there are factors warranting the application. Section 60 then sets out what the Court weighs.

New South Wales is also the only Australian jurisdiction with notional estate provisions. Where property passed out of the deceased's hands otherwise than through the estate — a transfer before death, a jointly held property that passed by survivorship — the Court can in defined circumstances designate it notional estate and order against it, within limits on how far back it reaches.

Time limits, and what it costs to find out

Under section 58 of the Succession Act 2006 (NSW) a family provision application runs to a strict time limit from the date of death, unless the Court otherwise orders on sufficient cause being shown. A validity challenge is not governed by that section, but delay has its own consequences: once an estate has been distributed, recovering it is a separate and harder exercise. Establish the date of death and how far the administration has gone before anything else; whether a grant has been made is part of that, and is covered under applying for probate.

Costs are in the Court's discretion, and it is not the rule that the estate always pays: an unsuccessful applicant can be ordered to pay the estate's costs, and what is spent comes out of what there is to divide. The Court's practice in the Equity Division is to refer these proceedings to mediation.

Whether any of this fits is a question about the facts — the will, the file it came from, the medical records, and the relationship to the person who died. A web page cannot answer it. We quote per matter, in writing, before work starts, with disbursements — filing fees, searches and any expert report — and GST identified separately from our professional fees. Formal costs disclosure under the Legal Profession Uniform Law follows on engagement.