Only citizens and permanent residents of either Canada or the United States are eligible for the NEXUS program. Applicants must have lived in one of these countries continuously for the last three years. Authorities will check applicants' documentation, run background checks, and take fingerprints, photographs and digital iris photographs. Applicants must also pay a fee, which is waived for applicants under 18 years of age. Applicants who pass these checks are issued a NEXUS card, which is valid for five years.