22 C.F.R. § 51.52

(a) A person who is exempt from the payment of passport fees under this section may obtain a passport book only for no charge. A passport card will not be issued for no charge to the individuals exempt from the payment of passport fees under this section.

(b) The following persons are exempt from payment of passport fees except for the passport execution fee, unless their applications are executed before a federal official, in which case they are also exempt from payment of the passport execution fee:

(1) An officer or employee of the United States traveling on official business and the members of his or her immediate family. The applicant must submit evidence of the official purpose of the travel and, if applicable, authorization for the members of his or her immediate family to accompany or reside with him or her abroad.

(2) An American seaman who requires a passport in connection with his or her duties aboard a United States flag vessel.

(3) A widow, widower, child, parent, brother or sister of a deceased member of the United States Armed Forces proceeding abroad to visit the grave of such service member or to attend a funeral or memorial service for such member.

(4) Other persons whom the Department determines should be exempt from payment of passport fees for compelling circumstances, pursuant to guidance issued by the Department; or

(5) Other categories of persons exempted by law.