Several forms of will are recognized in the United States, with each individual state having its own rules on what constitutes a valid will, and under what circumstances. While a standard, attorney-prepared will that is typed up and signed before witnesses will usually be valid, other forms of wills have their own rules.
A standard will is a formal document that is either handwritten, typed or printed from a computer. It will identify itself as a will, list the property to be bequeathed and the beneficiaries who will receive each item, and be signed at the bottom. In many cases, the document will be dated and declare any previous wills and codicils invalid, to prevent confusion over which is the “last will and testament.”
A holographic will is a document that has been handwritten by the testator, who is the person making the will. A holographic will may have been signed by the testator, but it will lack some or all of the required number of witness signatures. As a result, its validity may be called into question. Some states do not recognize a holographic will as a valid will.
A self-probating will is a will that conforms to all the state's requirements for a valid will but in addition, it has been submitted to the probate court by the testator. The document will be accompanied by a signed affidavit by each of the witnesses declaring that the testator signed the will in front of them without any form of duress, he was competent at the time, and he asked the witnesses to act as witnesses.
Codicils are not full wills in their own right. Instead, they are documents that alter existing wills in a small way, replacing only the specific portion of the will the codicil refers to and leaving the remainder intact. As a result, codicils are less expensive to create but may cause additional delays and expense when the will reaches probate, as both the will and the codicil must be probated.