20 CFR § 404.720 - Evidence of a person's death.
(a) When evidence of death is required. If you apply for benefits on the record of a deceased person, we will ask for evidence of the date and place of his or her death. We may also ask for evidence of another person's death if this is needed to prove you are eligible for benefits.
(b) Preferred evidence of death. The best evidence of a person's death is -
(1) A certified copy or extract from the public record of death, coroner's report of death, or verdict of a coroner's jury; or a certificate by the custodian of the public record of death;
(2) A statement of the funeral director, attending physician, intern of the institution where death occurred;
(3) A certified copy of, or extract from an official report or finding of death made by an agency or department of the United States; or
(4) If death occurred outside the United States, an official report of death by a United States Consul or other employee of the State Department; or a copy of the public record of death in the foreign country.
(c) Other evidence of death. If you cannot obtain the preferred evidence of a person's death, you will be asked to explain why and to give us other convincing evidence such as: the signed statements of two or more people with personal knowledge of the death, giving the place, date, and cause of death.