 The USCIS website, in the Employer section, Employer Bulletins, lists the limited requirements and allowed instances for reverification.For U.S. citizens, I-9s are valid continuously unless a break of more than a year of employment occurs.International employees on F-1 (student), H-1B (specialty occupation), or J-1 (exchange visitor) visas must have their I-9 reverified each time their visa has expired with a new work authorization permit (renewed visa with work authorization, EAD, Permanent Residence Card, etc.