To know if a will is valid, check four things: the person who signed it was at least 18, understood what they were doing, signed it voluntarily, and followed their state’s execution formalities, which in most states means signing in front of two adult witnesses who then sign the document themselves. If any of those four is missing, the document can be thrown out no matter how carefully the rest was handled.
Each requirement has details that trip families up. A witness who was also a beneficiary, a signature made during advanced dementia, a will that was never formally revoked but got replaced by a newer one, a spouse who was written out but has a statutory right to inherit anyway. The sections below walk through what to look at.
Age and Mental Capacity
Nearly every state requires the testator (the person making the will) to be at least 18. A few states carve out exceptions for emancipated minors or active-duty service members, but those exceptions are narrow. A will signed by someone under 18 who doesn’t qualify is void.
Age alone isn’t enough. The testator also needs “testamentary capacity” at the moment of signing. That means understanding four things: that the document distributes their property after death, what they generally own, who their close relatives and natural heirs are, and how the pieces fit together into a plan.1Legal Information Institute. Testamentary Capacity The bar is not high. Mild memory problems or early cognitive decline don’t automatically disqualify someone, because the test looks at whether they grasped the big picture on the day they signed, not whether their memory was intact generally.
Capacity questions come up most when a will is signed during declining health. The relevant question is always the testator’s state of mind on the specific day of execution, not their condition weeks before or after.
Signature and Witnesses
A standard will has to be in writing. Courts rely on the physical document to determine what the testator wanted, and testimony about what someone “meant to do” cannot substitute for it.
The testator has to sign. Most states are flexible about what a signature looks like. Someone who physically cannot write their full name can make an “X” or another mark, as long as it is witnessed. Some states allow another person to sign for the testator, but only in the testator’s presence and at their explicit direction.2Legal Information Institute. Wills – Signature Requirement
Then witnesses have to sign. The typical requirement is two witnesses who watch the testator sign, or who hear the testator acknowledge an already-made signature, and then sign the document themselves. Witnesses exist for one reason: to confirm later, if anyone asks, that they personally saw the testator execute the will. They don’t need to read the will or know what it says.
The Interested Witness Problem
Witnesses are supposed to be disinterested, meaning they have no financial stake in the will. When a beneficiary signs as a witness, states handle it differently. Under older “purging” statutes still in force in some states, the will stays valid but the gift to that witness gets wiped out, and their share passes to the other beneficiaries or heirs. Some states with purging rules soften the effect by letting the interested witness keep the smaller of their gift under the will or what they would have inherited without a will.
Many states that adopted the Uniform Probate Code have dropped the interested witness penalty entirely, on the theory that undue influence can be handled through separate litigation if it comes up. In those states, a beneficiary can witness and still inherit. The safe practice everywhere is to pick witnesses who aren’t named in the will.
Voluntary Signing
A will that meets every formal requirement can still be invalidated if the testator didn’t sign it freely. Courts look at three threats: undue influence, fraud, and duress.
Undue influence is the most commonly alleged ground for contesting a will.3Legal Information Institute. Will Contest It happens when someone in a position of trust or power over the testator manipulates them into signing a will that benefits the manipulator rather than reflecting the testator’s real wishes. The recurring pattern involves a caregiver or adult child who isolates an aging parent from the rest of the family and steers the estate plan. Courts weigh the relationship, the testator’s vulnerability, and whether the alleged influencer helped draft or arrange the signing.
Fraud is deception: tricking the testator about what a document says, or lying about a family member to get that person cut out. Duress is coercion: forcing the testator to sign through threats. In both cases, the signature isn’t truly voluntary, and the will can be thrown out.
Handwritten, Oral, and Electronic Wills
Not every will comes out of a lawyer’s office. Three alternative formats have their own validity rules, and each is more fragile than a standard witnessed will.
Holographic Wills
A holographic will is handwritten by the testator instead of typed and formally witnessed. Not all states recognize them. States that do generally require the will to be written and signed in the testator’s own hand, though they disagree on how much of the document needs to be handwritten. Some demand the entire document; others accept a will as long as its key provisions are in the testator’s handwriting.4Legal Information Institute. Holographic Will Because there are no witnesses, proving a holographic will in probate can require handwriting analysis or testimony from people familiar with the testator’s writing, which turns contested cases into expensive fights over penmanship.
Oral Wills
A nuncupative will is spoken rather than written. Most states don’t recognize them. The few that do restrict them to extreme situations, like a deathbed statement or a service member during active military service.5Legal Information Institute. Nuncupative Will Where allowed, oral wills usually cover only personal property, not real estate, and typically require two or more witnesses to the spoken words. Some states require the will to be reduced to writing within a short window, sometimes as few as six days.
Electronic Wills
A growing number of states now recognize electronic wills that are created, signed, and stored digitally. The Uniform Electronic Wills Act, developed by the Uniform Law Commission, lets a testator use an electronic signature with two witnesses attesting electronically. Adoption is uneven, and states that allow electronic wills often add their own rules on identity verification and tamper-proof storage. Before relying on a digital will, check whether your state has actually enacted authorizing legislation. A digital document that doesn’t match your state’s rules is no more valid than a napkin sketch.
Does a Will Need to Be Notarized?
In most states, no. A will is valid if it meets the execution formalities above, and a notary stamp doesn’t change that.
What notarization does is create a “self-proving affidavit,” a separate sworn statement signed by the testator and the witnesses in front of a notary public.6Legal Information Institute. Self-Proving Will The affidavit doesn’t make the will valid. It just simplifies probate. Without one, the court may have to track down the witnesses and have them testify that they watched the signing. With one, the court can accept the will based on the notarized statement alone, which matters when witnesses have moved, become incapacitated, or died.
Adding a self-proving affidavit is one of the cheapest steps you can take to smooth things out for your family later. Notary fees for this kind of document are typically modest, often under $15, and many estate planning attorneys include the affidavit as a standard part of will preparation.
Spousal Rights That Override a Valid Will
A will can be valid in every formal respect and still fail to control the whole estate if it shortchanges the surviving spouse. Most states give a surviving spouse a statutory right to claim a minimum share regardless of what the will says.
In “elective share” states, the surviving spouse can reject whatever the will provides and take a fixed portion of the estate instead, often around one-third. The exact percentage and calculation vary by state, and some states scale the share to the length of the marriage. In community property states, the protection works differently: each spouse already owns half of what was acquired during the marriage, and the testator can only give away their own half through a will. Either way, a will cannot fully disinherit a surviving spouse, no matter how clearly the testator tried to.
Was the Will Ever Revoked?
A will that was valid when signed may no longer be in effect by the time the testator dies. There are two basic ways to revoke a will: executing a new one or physically destroying the old one.
A later will that expressly says it revokes all prior wills does exactly that. If the new will doesn’t include revocation language but covers the entire estate, courts generally presume it replaces the earlier document. If the new will only partially overlaps with the old one, both remain in effect where they are consistent, and the newer provisions control where they conflict.
Physical destruction also works. Burning, tearing, or shredding a will with the intent to revoke it makes it invalid. A will found torn in half after the testator’s death creates an inference of revocation, though that inference can be rebutted.
For small changes, a codicil amends specific provisions without replacing the will. A codicil has to meet the same execution requirements as the will itself: signed and witnessed the same way. People use codicils to swap an executor, adjust a specific gift, or fix an error. For anything more than a minor edit, drafting a new will and expressly revoking the old one is usually cleaner.
Challenging a Will You Think Is Invalid
Who Can File
Not just anyone can contest a will. You need legal “standing,” which means you have to be someone who would be financially affected by the outcome. That typically means people named in a prior version of the will, people who would inherit under state intestacy laws if the will were thrown out, and in some cases creditors of the estate. A neighbor who thinks the will is unfair or a distant relative who was never going to inherit generally cannot bring a challenge.
How Long You Have
Every state sets a deadline for contesting a will after it has been admitted to probate. The deadlines are short, often measured in months. Once the window closes, the will stands even if there were real grounds to challenge it. Some states pause the deadline for minors or people who were legally incapacitated during the filing period, and courts may extend it if fraud or concealment kept someone from discovering the grounds. Those exceptions are narrow, and waiting is one of the most reliable ways to lose the right to contest.
No-Contest Clauses
Some wills include a no-contest clause saying that any beneficiary who challenges the will forfeits their inheritance.7Legal Information Institute. In Terrorem Clause These clauses are designed to deter litigation and mostly work: a beneficiary with a real gift on the line has to weigh losing everything if the challenge fails. Most states enforce them, but not absolutely. Several states carve out an exception for challenges brought in good faith with probable cause, meaning the beneficiary had reasonable evidence the will was actually invalid. At least one state refuses to enforce these clauses at all. If the will you are thinking about challenging contains one, get legal advice before filing anything.
What Happens If a Will Is Thrown Out
When a court invalidates a will, it looks for the next best evidence of what the deceased wanted. If an earlier valid will exists, the court reinstates it and follows its instructions.
If there is no prior valid will, the estate goes into “intestacy,” and the state’s default inheritance rules take over. Those rules prioritize surviving spouses and children, then move outward to parents, siblings, and more distant relatives in a statutory order that varies by state. Intestacy laws try to approximate what most people would have wanted, but they are blunt. They do not account for estranged relatives, unmarried partners, close friends, or charitable intentions. A will that meets the validity requirements above is the only reliable way to direct where your property actually goes.