Unlike other legal documents, a will generally isn't valid unless two adult witnesses watch the will-maker sign it. The witnesses must know that the document is intended to be that person's will, and they must also sign the document themselves.
Why this extra level of formality and caution, when it's not required for other important documents such as contracts or promissory notes? The simple answer is that by the time a will takes effect, the person who signed it is no longer around to say whether or not the document that's being presented to the probate court is really that person's will. But if there are witnesses, they can come to court and testify that the will maker stated the document was the will maker's will, and appeared to be of sound mind and not under any undue influence.
While state laws on the requirements of a will can vary, almost all states require two disinterested (see below) witnesses.
When you're talking about a will, a notarized signature is not the same thing as a witnessed signature. Only two states, Colorado and North Dakota, currently allows will makers to choose to have their signatures notarized instead of witnessed.
That said, it's very common to take an extra step of attaching notarized sworn statements from your witnesses. These statements are called self-proving affidavits, and can help your loved ones save a few steps later on during the probate process. If you make your will self-proving by attaching these statements, your witnesses won't need to come to court after your death to testify. But self-proving affidavits are not necessary; your will is valid without them, so long as it meets the witnessing and other requirements. ((For a more general overview of the requirements for a valid will, see How To Determine if a Will is Valid.)
Not everyone can be a witness to a will. The requirements vary from state to state, but here are the basic rules:
Each witness must be a legal adult, which usually means 18 or over.
Most states require that witnesses be "disinterested"—in other words, that they do not stand to inherit under the terms of the will. A beneficiary's spouse might also be disqualified from serving as a witness in some states. If a beneficiary does serve as a witness, the will's gift to that person could be declared void by a court. The rest of the will would remain in effect.
It's usually not a problem for the lawyer who drew up a will to also serve as a witness when the will is signed, even if the lawyer is also named as the executor and will profit later from charging fees for the executor's work.
Every state requires that a certain procedure be followed when a will is signed. Here's the typical procedure:
Variations can exist. In some states, the witnesses don't have to be in the same room when they sign the will. In others, they don't even have to watch the will-maker sign, as long as the will maker later tells the witnesses that he or she signed the document. Or the witnesses may be allowed to watch the will-maker sign the will, and sign it later themselves.
The witnesses must know that the document is a will, or the document won't be valid. In one case, the brother of an elderly man asked two men to "witness something" the man was about to sign, but didn't know it was a will. When the will was later challenged in probate court, the judge threw it out.
Do all wills need to be witnessed? In all cases, it's best to have witnesses. Some states will only accept wills that have been witnessed. However, in some states, certain unwitnessed wills can still be valid. About half of the U.S. states accept "holographic wills," which are wills that are written entirely or partially (depending on the state's laws) in the deceased person's handwriting and not witnessed. Some states require that they be dated as well.
If you find a loved one's handwritten will that was unwitnessed, you might be in luck, depending on whether your state accepts holographic wills. However, if you're about to make a will, it's always best to have it properly witnessed, regardless of what state you live in. A properly witnessed will is simply more ironclad.
To get help making a will and getting it witnessed, you can certainly turn to a lawyer, but it's not always necessary. You can also use a reputable self-help service such as Nolo's bestselling Quicken WillMaker to make your own will.