How to Write a Valid Will (and What Happens in Probate)

Most people avoid thinking about their will until something forces the issue: a new child, a diagnosis, a friend's messy estate dispute, or simply the quiet discomfort of knowing the paperwork isn't done. That discomfort is nothing compared to the cost of not writing one, or writing one poorly. After fifteen years reviewing estates in and out of probate court, I can tell you the wills that cause the least grief are rarely the most elaborate. They are the ones that follow the formalities carefully and say, in plain language, exactly what the person meant.

This piece covers what makes a will legally valid, the mistakes that get wills challenged, what probate is and why it exists, how long it takes and costs, and what happens when there is no valid will at all.

What Makes a Will Legally Valid

Every legal system has its own formalities, but nearly all test a will against the same three questions: did the person have capacity, did they follow the required signing and witnessing procedure, and does the document clearly express their intent.

Testamentary Capacity

Testamentary capacity is the legal threshold for whether someone is mentally competent to make a will, and it is a lower bar than many assume. The person generally needs to understand, at signing, that they are distributing property after death, have a general sense of what they own, and recognize who would naturally be expected to inherit, even if they leave that person out. Someone can have dementia or be in hospice care and still have capacity during a lucid, well-documented signing session, because capacity is judged at the moment of execution, not overall health.

This is why estates involving elderly or ill testators benefit from a contemporaneous capacity note — a short letter from the treating physician confirming the person understood what they signed. It costs little and can shut down a challenge before it starts.

Signing and Witnessing Requirements

This is where otherwise well-intentioned wills fail most often. Formalities differ by jurisdiction, but the core requirements recur: the will must be in writing, signed by the testator, and signed by a specific number of witnesses, commonly two, present at the same time and watching the testator sign or acknowledge the signature — typically in the testator's presence, not mailed in afterward.

A frequently overlooked rule is that a witness generally should not be a beneficiary, or married to one. An "interested witness" doesn't always void the whole document, but in many places it voids that witness's own inheritance, or shifts the burden onto them to show no undue influence occurred. Some jurisdictions permit remote or electronic witnessing under narrow conditions, but treat this as the exception, not the default. Notarization is separate: some places use it for a "self-proving affidavit" that speeds up probate later, but it does not replace the required live witnesses.

Clear Testamentary Intent

The document also has to read as a will: a deliberate statement of how property should be distributed after death, not an ambiguous letter or a casual conversation someone remembers. Courts look for language that unmistakably shows intent, clearly identifies the property and people involved, and revokes prior wills. Vague phrases like "I want my things to go to whoever needs them most," or naming "my nephew" when there are several, invite the exact dispute a will is meant to prevent.

Common Mistakes That Get Wills Challenged

Certain errors show up again and again in contested estates. Improper witnessing is the single most common technical defect: a missing signature, a witness who signed at the wrong time, or a witness who also stands to inherit. Undue influence claims arise when a will suddenly favors a new caregiver or late-in-life partner over siblings previously treated equally, especially if that person helped arrange it; a drastic change made through someone controlling the testator's daily life, with isolation from family, draws scrutiny. Ambiguous language — vague bequests, percentages that don't add to 100, or loosely described property — forces a court to interpret intent rather than execute it. And outdated beneficiary designations quietly undermine a well-drafted will, since certain assets pass by contract, not by the will.

Related planning tools often prevent these problems before they start. A living trust can move significant assets outside probate entirely, and a properly executed power of attorney lets someone you trust manage your finances if you become incapacitated — a problem a will does nothing to solve, since it only takes effect after death.

What Probate Actually Is

Probate is the court-supervised process of authenticating a will, appointing someone to administer the estate, paying debts and taxes, and distributing what remains to beneficiaries. It exists because a will is just paper until a court confirms it is genuine and properly executed. Probate also gives creditors a window to make claims, gives the executor authority to close accounts or sell property, and creates a public record of ownership that matters for real estate titles and banks.

Not everything goes through probate. Jointly owned property with survivorship rights, accounts with valid beneficiary designations, and assets held in a properly funded trust typically bypass it, which is why people use trusts and careful account titling alongside a will rather than instead of one.

How Probate Timelines and Costs Generally Work

Timelines vary by jurisdiction, estate size, and whether anyone contests the will, but a broad pattern holds almost everywhere: a simple, uncontested estate often resolves within several months to a year, while estates with property in multiple locations, business interests, or family conflict routinely stretch to two years or longer.

Costs generally fall into a few categories: modest court filing fees, executor compensation set by statute or custom, and professional fees for the attorney and accountant, scaling with complexity and, in some jurisdictions, with estate value. Contested estates are dramatically more expensive, since litigation can consume a meaningful share of the estate — the practical argument for a clean, well-witnessed will over a homemade one.

Dying Without a Will: Intestate Succession

When someone dies without a valid will, their estate is distributed under intestate succession, a statutory formula that assigns assets to relatives in a fixed order regardless of what the deceased might have wanted. Details differ by jurisdiction, but the logic is similar almost everywhere: a surviving spouse and children typically receive the largest shares, with parents, siblings, and more distant relatives inheriting only if closer relatives don't survive.

Intestate succession has no mechanism for personal wishes. It cannot leave anything to a close friend, an unmarried partner in many jurisdictions, a stepchild never formally adopted, or a favorite charity, and it cannot reward a family member who provided years of caregiving. Nor can it name a preferred guardian for minor children — that decision instead falls to a court weighing the available family members, sometimes with results a parent would never have chosen. Dying intestate doesn't mean the state keeps everything, as popular myth suggests, but it does mean a rigid formula, not your judgment, decides who gets what.

Key Takeaways

• A valid will generally requires testamentary capacity, proper signing and witnessing by disinterested witnesses, and clear, unambiguous language expressing intent.
• Improper witnessing, undue influence, vague drafting, and outdated beneficiary designations are the most common reasons wills get challenged or partially overridden.
• Probate is the court process that authenticates a will, resolves debts, and formally transfers assets; it typically takes months to over a year and costs scale with complexity and conflict.
• Dying without a valid will triggers intestate succession, a statutory distribution formula that ignores personal relationships and unwritten wishes.
• Tools like living trusts and powers of attorney complement a will by addressing incapacity and by moving specific assets outside probate altogether.

Because will formalities and probate procedures vary significantly from one country and state to the next, this article is offered as general worldwide legal education and should not substitute for advice from a qualified estate planning attorney licensed in your jurisdiction.

Eleanor Whitfield is Law Elite Network's Estate Planning & Probate Editor. She holds an LL.M. in estate and trust law and has spent more than fifteen years advising families and reviewing contested estates.