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Missouri Will Requirements: 5 Legal Rules You Can’t Ignore


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Making sure your will is actually valid is critically important. Not only do you want your wishes honored, you want to make sure your assets aren’t distributed according to intestacy laws. There are specific requirements you have to follow to make sure your will is valid. It is always best to have your will drafted by a skilled attorney. 

The estate planning attorneys at Mark Harford Law help you draft your will correctly and build a comprehensive estate plan that works for you and your family.   

1. The Testator Must Be at Least 18 and of Sound Mind

Missouri law requires that the person making the will, called the testator, be:

  • At least 18 years old, or
  • Legally emancipated, and
  • Of sound mind at the time the will is signed.

“Sound mind” means the testator must understand:

  • The nature and purpose of a will
  • The property they own
  • Who their natural heirs are
  • How the will distributes their assets

If the will gets challenged, mental capacity is often one of the main reasons it happens. If you make sure the testator has capacity and properly document it, you can head off any dispute before it happens. 

2. The Will Must Be in Writing

Missouri almost never accepts oral wills, with very narrow exceptions. Even then, it requires imminent death a number of other rules that are rarely satisfied. 

To be valid, a Missouri will must be:

  • Written, either typed or handwritten
  • Clear and legible
  • Signed by the testator

Typed wills are the most common and easiest to validate. Handwritten wills, known as holographic wills, are allowed in Missouri only if they are entirely in the testator’s handwriting and signed. However, there will likely be a challenge to them, so typed is much better. 

3. Two Competent Witnesses Must Sign the Will

Two competent witnesses are required to sign the will. They have to observe the testator sign the will, or the testator can acknowledge their prior signature. The witnesses then have to sign it themselves.

Key rules for witnesses include:

  • They must be at least 18 years old.
  • They must be mentally competent.
  • They should not be beneficiaries under the will.

4. The Testator Must Sign the Will (or Direct Someone to Sign for Them)

A will is not valid unless it is signed. Missouri allows:

  • The testator to sign the will personally, or
  • Another person to sign for them, if the testator tells them to and it is signed in the testator’s presence

This can be complicated, with a lot of exceptions and other rules. It is best to have an attorney help with this part of the process. 

5. A Self-Proving Affidavit Strongly Strengthens the Will

Although not required, Missouri strongly encourages the use of a self-proving affidavit. This is a notarized statement signed by the testator and witnesses confirming that:

Lawyer is showing documents to the client
  • The testator signed the will voluntarily
  • The witnesses observed the signing
  • All parties were competent at the time

Why These Requirements Matter

Missouri probate courts take will validity seriously. If a will fails to meet statutory requirements, the court may:

  • Reject the will entirely
  • Apply Missouri’s intestacy laws
  • Trigger disputes among heirs
  • Delay the distribution of assets

A properly executed will ensures your wishes are honored and your loved ones avoid unnecessary conflict.

Draft Your Will the Right Way: Don’t Ignore These Important Rules

Understanding these basic rules can help you get started, but the right estate plan takes more than just a good will. Learn more about how a skilled lawyer can help you customize a plan that best fits your needs. 

Let the dedicated estate planning attorneys at Mark Harford Law help you. Contact us today for a consultation.