In California, a handwritten holographic will can sometimes be valid without witnesses. In Washington, Oregon, Florida, and many other states, a typed will signed without the required witnesses usually fails, which can change who inherits and who handles the estate.

Picture a December kitchen-table signing. A widowed retiree prints a will, signs it, and asks one adult child to watch. No second witness. After death, the family takes the document to probate court expecting it to control everything. The court may refuse to admit it as a valid will. If that happens, the estate is distributed under the state's intestacy law instead of the document's instructions. That can mean shares going to relatives the person did not choose, and an executor named in the paper may have no authority at all.

The general rule is that a formal will must meet a few basic requirements:

• the person making it had testamentary capacity
• the will was made voluntarily
• it was signed by the will-maker, or by someone else at their direction
• it was witnessed with the number and method the state requires, often two witnesses

Some states also require the witnesses to sign in the testator's presence or within a short time after watching the signing. A few states accept harmless error if there is clear evidence the document was meant to be a will. Others do not.

A separate issue is whether a witness is an interested witness who inherits under the will. In some states, that does not void the whole will, but it can void that witness's gift.

A self-proving affidavit helps probate move faster, but it does not replace missing witnesses. If the witness rules are not met, the paper may be treated as no will at all.