HellFile

A HellFile is a type of document that exists in Hell, specifically in Mephistopheles' main office.

Canon Media
Within the original Welcome to Hell comic, and later the film, Mephistopheles reveals such documents when Sock arrives in his office shortly after his death. He has access to Sock's HellFile, but does not show anything in it to the audience; he does, however, give Sock access to Jonathan Combs' HellFile so he can prepare for his first assignment as a personal demon.

UC Stories
Within the Universal Clarification Series, a HellFile is relatively the same as in canon media, but may have more information on any specific individual that Mephistopheles has readily accessible, giving him the power to hold superiority over one's soul. However, he cannot obtain this "bonus information" unless any living person is confirmed for their soul winding up in his possession as opposed to Providence's in Heaven.