Form I-94 (Arrival/Departure Record) documents a lawful admission to the U.S. in a specific status and any defined expiration of that status in the U.S. When a nonimmigrant is admitted to the U.S. he or she is issued a small white card (Form I-94) which is normally stappled in or placed inside his or her passport. The "I-94 card" (as it is commonly referred) is a very important document. When departing the U.S. an immigration official will often wish to confirm that an individual has maintained status, and will do so by referencing the I-94 card.
For many types of nonimmigrant visa classifications the I-94 card will be issued with a defined expiration. Individuals holding these types of I-94 cards must depart the U.S. or extend or change their status before the expiration on the I-94 card.
For other types of nonimmigrant visa classifications including F and J, the I-94 card should indicate the recognized and proper visa status as well as "D/S" which stands for "Duration of Status". These I-94 cards do not have a defined expiration date, and remain valid provided that all conditions of lawful status in the U.S. are met.
When an application to change or extend nonimmigrant status is approved, the USCIS will issue Form I-797 containing an I-94 coupon (in the lower-right of the form) which should be torn off and stapled into the applicant's passport as would an I-94 card received when admitted to the U.S.
Beginning April-May 2013, the paper I-94 will no longer be issued at air and sea crossings. Instead a stamp will be placed directly in the passport. You will still need to ascertain that the correct information has been entered by Immigration at the port of entry, and you have therefore been admitted to the U.S. under the proper status. To retrieve I-94 data, as well as the ability to print an I-94 facsimile for applications and benefits, please visit www.cbp.gov/I94.