The Department of Homeland Security (DHS) issues Form I-94, Arrival/Departure Record, to aliens who are:
All persons need a Form I-94 except U.S. citizens, returning resident aliens, aliens with immigrant visas, and most Canadian citizens visiting or in transit. Air and sea travelers will be issued I-94s during the admission process at the port of entry.
A Customs and Border Protection (CBP) officer attaches Form I-94 to the nonimmigrant visitor’s passport upon entry to the U.S. The visitor must exit the U.S. on or before the departure date stamped on the Form I-94. This is the “Admit Until Date” on the electronic Form I-94. The Form I-94 number also is known as the Departure Number or Admission Record Number.
As of April 30, 2013, most Arrival and/or Departure records are created electronically upon arrival.
If you cannot get your Form I-94 from the CBP website, you may file Form I-102, Application for Replacement/Initial Nonimmigrant Arrival-Departure Record, with USCIS.