A written will must be signed at the end; a testator unable to write may make an X, and such a mark is considered a valid signature. In the U.S. generally, two, and in some states three, persons must witness the will, that is, they must sign the will as witnesses to the signature of the testator. In most states the signing must be done in the presence of witnesses, and the testator must state that the document being signed is his or her will. The witnesses need not be acquainted with one another and may sign at the same time or at separate times, depending on the statutory requirements of the state in which the will is executed; thus, the signature may, in most states, be written in the presence of one witness and acknowledged later by other witnesses.
All witnesses to a will must be "competent." A witness is considered incompetent if he or she is a beneficiary under the instrument; if one of the necessary witnesses is a beneficiary, the will is void. To remedy such situations it has generally, although not universally, been provided by statute that a bequest to a subscribing witness shall be void and that the will shall otherwise be valid.