In New York State, they are only valid if they are made by members of the armed services during an armed conflict. The handwritten will must be entirely in the testator’s (deceased person’s) handwriting. These types of wills are only valid for one year after the person ceases serving.

After the person who wrote the will has passed away, it’s more difficult to prove the validity of a holographic will in probate court. If you’re an executor submitting a holographic will to probate, you must show that entire will, or at least all the significant parts, is in the handwriting of the deceased person.

You also need proof the testator had the mental capacity to write the will and the will must contain the testator’s wish to disburse personal property to beneficiaries.

Different states have different requirements, so if you’re not in New York State, check with an attorney in your state.