The most important error commonly made by foreigners after entry into the United States is confusing the visa, a machine-readable visa stamp bearing a photo issued into the traveler’s passport at a US Embassy abroad, with the I-94 entry/departure record, which used to be a card stapled into the passport at a US airport or border post when the traveler was admitted, and is now primarily an electronic record that must be retrieved from www.i94.cbp.dhs.gov. US Customs & Border Protection ("CBP") shifted to electronic entry records as of April 26, 2013, so most travelers admitted after that date will have to retrieve and print out the electronic I-94.
A visa is an entry document, which must be valid for admission when traveling from abroad and seeking lawful admission into the United States at a Port of Entry. An I-94 is a status document, which defines the traveler’s visa status once inside the United States, and the length of stay permitted. Once a traveler is admitted to the United States, dates on the visa do not define how long the traveler is allowed to stay; the I-94 is the controlling document.
For most temporary travelers, the I-94 card or electronic printout will show two important dates: the date of admission, which should match the date of the entry stamp in the passport, and the date the authorized period of stay ends. All US airports are now using the electronic system, so travelers must be vigilant to make sure the inspecting officer does not make typos, spelling or transcription errors when entering the travelers names, date of birth, or class of admission, as these are fields necessary to retrieve the electronic record.
Many travelers with work visas may have multiple notices of approval from USCIS with “replacement I-94s” to indicate a change or extension of status. Even if you have one or more of these, do not discard the I-94 card or printout documenting your last admission at a Port of Entry.
Some types of travelers (primarily students) receive an I-94 marked “D/S” meaning "Duration of Status,” instead of one that specifies a fixed end date. “D/S” refers to another, secondary status document that will determine when the lawful period of stay ends. For F-1 and M-1 students, the secondary status document is a Form I-20, issued by a US school authorized to enroll foreign students in a full-time course of study. For J-1 exchange visitors, the secondary status document is a Form DS-2019, issued by a program sponsor authorized by the U.S. Department of State.
Except for students who have quit their program and are no longer maintaining valid visa status, most are entitled to a grace period. Upon completion of the authorized course of study or practical training, F-1 students are allowed a grace period of 60 days during which they may remain in the United States. J-1 exchange visitors and M-1 vocational students have a grace period of 30 days.
Some visitors from countries that participate in the Visa Waiver Program- who are allowed to come to the U.S. as visitors without applying for a visa – are admitted for 90 days only, and may not extend their stay. Travelers visiting under the Visa Waiver Program were the first to be given only electronic I-94 records; after successful rollout of the electronic I-94 program for VWP entrants, it was expanded to include all other nonimmigrants.
There are many subtleties to status documents, and many situations where the end date of your lawful period of admission will not match the petition end date or the ending validity date of your visa. If you have questions about your own status documents, consult an immigration attorney and bring the original documents for clarification.