To find a person's date of death, one needs to gain access to the Death Master File, maintained by the Social Security Administration. While the SSA maintains it, access to this file must be acquired by other means, such as contacting the National Technical Information Service.
As of July 2015, the National Technical Information Service may be contacted through the sales department at 1-800-553-6847. Their website is located at NTIS.gov. People can also conduct a date of death search by using paid sites such as Ancestry.com, which provides the same information maintained by Social Security. Information may also be available on family tree sites, such as MyHeritage.com.