Nonimmigrant Information System compiles and maintains information collected from nonimmigrants by United States Department of Homeland Security (DHS) Form I-94, also known as the Arrival-Departure Record, which asks for dates of arrival and departure as well as limited demographic information, such as name, gender, nationality, and Date Of Birth.
Each time a nonimmigrant enters the United States, the arrival portion of the I-94 Form is collected and the information is entered into the data system. Conversely, each time a nonimmigrant leaves the United States, the departure portion is collected and the additional information is entered into NIIS. The arrival and departure records are then electronically matched, producing a single record that includes both the arrival and departure date.
Nonimmigrants arriving by air, land, or sea are required to complete Form I-94 with two important exceptions. Canadians who travel to the United States as tourists or on business generally do not need the I-94 Form. Also, certain Mexicans who have a nonresident alien Border Crossing Card, commonly known as a laser visa, may not require the I-94.