Written by: Attorney Scott Stork
TL;DR
Signing a document called a will doesn’t guarantee that a will is valid or that it will work as you intend.. In Missouri, a will has to meet specific requirements, and six common mistakes can quietly undo it: improper signing, missing or improper witnesses, letting the will go outdated, vague DIY language, failing to name a guardian for your children, and assuming the will controls assets that actually pass outside it, like retirement accounts and life insurance. A flawed will can be worse than none at all, because it creates false confidence while leaving real gaps. The good news is that all six are avoidable, and finding out whether your current will would hold up does not take long.
Somewhere in a drawer or a cloud folder is the will you set up a few years ago, probably online, probably after a big life moment like a new baby or a new house. You signed it, felt a wave of relief at finally handling it, and moved on. In every other part of your life you’re organized and thorough. This one you checked off and stopped thinking about.
Here’s the unsettling part worth considering for a moment: signing a document called a will does not guarantee it will actually work. Wills fail. Not because people are careless, but because a will has to meet specific legal requirements to be valid, and a document that misses even one of them can be thrown out entirely, sending your family into exactly the mess you meant to spare them. The false confidence a flawed will creates can be worse than having no plan at all.
The good news is that the mistakes that invalidate a will are well known and entirely avoidable. This article walks through six of the most common ones in Missouri, so you can find out whether the plan you already made would hold up when it counts.
What It Actually Takes to Create a Valid Will in Missouri
To create a will in Missouri that holds up, the document has to clear a short list of legal requirements. They aren’t complicated, but they aren’t optional either, and this is exactly where do-it-yourself wills tend to go wrong. Meeting all of the requirements is the difference between a document that directs your estate and one a court sets aside.
Missouri law asks for a few core things. You must be at least eighteen and of sound mind when you sign, meaning you understand what you own, who your natural heirs are, and what the document does. The will must be in writing. You must sign it, or direct someone to sign for you in your presence if you physically cannot. And it must be signed by at least two witnesses, who watch you sign and then sign themselves. Miss the witnessing step, or handle it improperly, and the whole document can fail regardless of how clearly it states your wishes.
There’s also the matter of proving the will later. Missouri allows a will to be made “self-proving” by adding a notarized affidavit from you and your witnesses at signing. It isn’t strictly required for validity, but without it, your witnesses may have to be tracked down years later to confirm the signing, which delays everything at the worst possible time. A properly executed will anticipates that problem and removes it.
Consider a busy professional who created a will online after his second child was born. He read it, printed it, and signed it at his kitchen table one evening. No witnesses were present, because the form’s instructions were buried and he was moving quickly. The document looks like a will, reads like a will, and sits in his files giving him a sense of security. In Missouri, without proper witnessing, it may not function as one at all.
That gap between “having a will” and “having a valid will” is the theme of everything that follows in this blog. A will is not valid because you meant it to be, or because it’s labeled that way. It’s valid because it was created and executed correctly. The six mistakes in the next sections are simply the most common ways that goes wrong, starting with the errors that trip up the most people: signing and witnessing.
Mistake #1 and #2: Signing and Witnessing Done Wrong
The two mistakes that void more wills than any others happen at the moment of signing. They’re procedural, not substantive, which is what makes them so cruel: the document can say everything correctly and still fail because of how it was executed.
The first is a signing problem. Missouri expects you to sign the will yourself, or to direct someone to sign for you in your presence if you physically can’t. That sounds simple, but the details trip people up. An unsigned will is not a will. A will signed in the wrong place, or a draft mistaken for the final signed version, can create the same result. With online and DIY documents, it’s common to end up with a printed form that was filled in but never properly executed, or executed in a way the form’s fine print didn’t adequately explain.
The second, is witnessing. Missouri requires at least two witnesses who observe you signing and then sign the will themselves. Skip them, use only one, or have people sign at different times without witnessing the actual signature, and the will can be invalidated no matter how clear your intentions were. There’s a further trap: a witness who also stands to inherit under the will can create complications, so the witnesses generally should be neutral parties, not the spouse or children who are named to receive assets.
Picture a professional couple who sat down one weekend to finally handle their wills. They printed the documents, signed them, and filed them away, satisfied it was done. No witnesses were present. Years later, if one of those wills is challenged or simply presented to a court, it may be treated as though it never existed, and their estate could pass under Missouri’s default rules instead of their actual wishes. They did the hard part, deciding what they wanted, and lost it on a formality no one flagged.
The takeaway is direct: the execution of a will is not a rubber stamp on the real work, it is part of the real work. A will drafted with perfect intentions and signed incorrectly accomplishes nothing. This is the single strongest argument against treating a will as a form to fill out alone, and the easiest mistake to prevent when the signing is handled properly the first time.
Mistake #3 and #4: An Outdated Will and Vague DIY Language
The next two mistakes don’t usually void a will outright the way a botched signing does. They do something quieter and sometimes worse: they leave you with a technically valid document that no longer says what you’d actually want, or says it so unclearly that your family ends up fighting over what you meant.
The third mistake is letting a will go stale. A will captures your life at the moment you signed it, but life doesn’t hold still. You have another child the will never mentions. You buy a home, exercise stock options, or take on a partnership interest that didn’t exist when you signed. You get married, divorced, or remarried. You move to Missouri from another state, where the rules that governed your old will may differ. Any of these can leave a valid document badly out of step with reality, distributing assets you no longer own, omitting people you’d never leave out, or naming an executor who’s no longer the right choice. The will works, mechanically. It just protects the wrong version of your life.
The fourth mistake is vague or contradictory language, the signature weakness of fill-in-the-blank documents. Online forms are built to be generic, and generic language invites interpretation. A clause that names beneficiaries ambiguously, contradicts another section, or fails to account for what happens if someone predeceases you can turn a simple estate into a contested one. For someone with real complexity in their assets, professional equity, blended assets, or children at different ages, boilerplate wording rarely captures the actual situation. The document reads fine on a quiet afternoon and unravels the moment it faces a real question.
Consider someone who set up an online will after a first child, then over the next eight years had a second child, bought a larger home, and accumulated significant equity through work. The will still reflects the life of a younger man with one child and a starter house. It’s valid. It’s also close to useless for the family he actually has now, and its generic language leaves genuine room for dispute among the people he most wanted to protect.
The takeaway is that a will is not a one-time task but a living document. Getting the words right, and keeping them current as your life and wealth grow, is as important as signing it correctly. A valid will pointed at the wrong life still fails the people it was meant to serve.
Mistake #5 and #6: No Guardian Named and Assets a Will Can’t Control
The last two mistakes are the ones with the highest stakes, because they touch the two things a professional with a young family and growing wealth most needs a will to handle: who raises the children, and what actually reaches them.
The fifth mistake is failing to name a guardian for minor children. This is the single most important thing a will does for a parent, and it’s the mistake estate planning attorneys widely consider the most common and most dangerous, sometimes because they never got that far in the form, and sometimes because two parents can’t agree on who the guardian should be. The consequence is stark. If both parents die without having named a guardian, a Missouri court decides who raises their children, choosing among family members who may petition, or appointing someone based on the court’s judgment rather than theirs. A decision this personal, made by a judge who never met your family, is exactly the outcome a will exists to prevent. Disagreeing with your partner about the choice is understandable. Leaving it to a judge that does not know your family is far worse.
The sixth mistake is assuming a will controls everything you own. It doesn’t. Several major assets pass outside your will entirely, by their own rules. Life insurance and retirement accounts go to whoever is named on the beneficiary form, no matter what your will says. Jointly owned property typically passes to the surviving owner automatically. Business interests may be governed by a partnership or operating agreement, or a buy-sell provision, that overrides your intentions. So you can write a careful will and still have your largest assets, an old 401(k), a life insurance policy, an equity stake, bypass it completely, landing with the wrong person or in a way that undercuts the plan.
Consider a professional who names his brother guardian and divides everything “equally between my children” in his will, then never updates the beneficiary on a substantial retirement account still listing his mother from a decade ago. The will is valid and thoughtful. The largest asset ignores it entirely.
The takeaway ties the two together: a will has to name a guardian to protect your children, and it has to be coordinated with the assets it doesn’t directly control. Getting one right and missing the other still leaves a serious gap where you least expect it.
How to Make Sure Your Will Actually Holds Up
Six mistakes sound like a lot to guard against, but they collapse into a single principle: a will works when it’s created correctly, kept current, and coordinated with everything around it. Each of the fixes below maps directly to a mistake, and none of them requires you to become an expert. They require the document to be done properly once, and then not abandoned.
Start with execution, because it’s the most fatal and the most preventable. The will must be signed and witnessed the way Missouri requires, with neutral witnesses and, ideally, a self-proving affidavit so no one has to reconstruct the signing years later. This alone puts you ahead of most DIY wills. Then address the language: clear, specific wording that names beneficiaries unambiguously and accounts for contingencies, rather than boilerplate that reads fine until it’s tested. For anyone with equity, a business interest, or blended assets, precise drafting is where a real plan separates from a form.
Name a guardian, and if you and your partner disagree, treat that disagreement as the reason to decide now rather than an excuse to wait. A hard conversation between two people who love their children is still infinitely better than a judgment handed down by a court that knows none of you. Then coordinate the assets your will doesn’t control. Review the beneficiary designations on your retirement accounts and life insurance so they match your intentions, and make sure business and jointly held assets are accounted for rather than quietly overriding your plan.
Two habits keep all of this intact. The first is keeping the plan current, revisiting it after a birth, a move, a marriage, a major purchase, or a jump in income, so it never drifts from your actual life. The second is recognizing that for someone building real wealth, a will is often the floor rather than the ceiling. A will still requires probate, and it can’t do everything a growing estate needs. Many professionals at this stage find that adding a trust and a coordinated estate plan fit their situation better, not because they’re wealthy already, but because they’re building toward it.
The takeaway is genuinely reassuring: you don’t have to fear these mistakes, you just have to close them. Done properly, a will stops being a source of quiet anxiety and becomes what you intended it to be, real protection for the people who depend on you.
Frequently Asked Questions
1. What makes a will valid in Missouri?
You must be at least eighteen and of sound mind, the will must be in writing, you must sign it, and at least two witnesses must watch you sign and sign it themselves. Miss any of these and the will can be invalidated.
2. Does a will have to be notarized in Missouri?
Not to be valid, but adding a notarized self-proving affidavit at signing means your witnesses won’t have to be located later to confirm it, which saves your family time and trouble.
3. Is an online will legal in Missouri?
It can be, if it meets every legal requirement, including proper signing and witnessing. The problem is that DIY wills often miss those steps or use vague language, which is what gets them thrown out.
4. How many witnesses does a Missouri will need?
At least two. They should watch you sign and then sign themselves, and they generally shouldn’t be people who inherit under the will, since that can create complications.
5. Can I write my own will in Missouri?
Yes, but writing it is the easy part. Executing it correctly and drafting language that holds up under a real challenge is where most self-made wills fall short. Polaris Estate Planning and Elder Law handles Missouri wills properly on our Missouri wills page.
6. What happens if my will is invalid?
It’s treated as though it doesn’t exist. Your estate passes under Missouri’s default intestacy rules, which may send your assets to people you wouldn’t have chosen and leave guardianship to a court.
7. Does a will cover all of my assets?
No. Life insurance, retirement accounts, jointly owned property, and business interests often pass outside the will by their own rules. Those have to be coordinated separately.
8. What happens if I don’t name a guardian for my children?
If both parents die without naming one, a Missouri court decides who raises your minor children, rather than you. Naming a guardian is the most important thing a will does for a parent.
9. How often should I update my will?
Revisit it after any major life change, a birth, marriage, divorce, move, large purchase, or significant income jump, and periodically even without one. An outdated will can be valid and still protect the wrong version of your life.
10. Is a will enough, or do I need a trust?
A will is a solid floor, but it still requires probate and can’t do everything. For families building real wealth, a trust often fits better. The right answer depends on your assets and goals.
Next Steps: Make Sure the Will You Have Actually Protects Your Family
The hardest part of estate planning is the part you’ve likely already done: deciding it matters. What trips up capable, responsible people isn’t intention. It’s the gap between having a will and having one that actually holds up, is correctly signed and witnessed, is current with your life, is clearly written, names a guardian, and is coordinated with the assets it doesn’t directly control.
You would never leave a major deal half-executed and assume it was binding. Your will deserves the same rigor, because the stakes, who raises your children and what reaches them, are higher than any deal you’ll close this year. A document that only looks finished can leave your family with the exact mess you meant to prevent, at the worst possible moment to discover it.
The reassuring part is that every one of these mistakes is avoidable, and finding out where your current will stands is quick. You don’t need to have it all figured out first. You just need to stop letting it slide to next quarter.
Ready to secure your family’s future or have a question about getting started? Call Polaris Estate Planning and Elder Law today.
St. Charles Office: (636) 202-1364
St. Louis County: (314) 470-8317
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