Form I-94 Application Guide
I-94/I-94W records all information about visitors arriving and departing the United States.
Visitors to the United States must apply for a visa to enter the country. This is except if they are citizens of one of 35 visa-exempt countries or have a machine-readable passport. Citizens from visa waiver countries are allowed to enter the United States for up 90 days without a visa. No matter if the visitor is coming to the United States under Visa Waiver Program or if he/she holds a visa, all visitors must fill out either Form I-944 (white) or I-94W(green).
Have you lost your Form I-94 in the United States? If you forget to return your Form I-94 when leaving the United States, it can be a problem. The file will remain open, and if you exceed the legal stay time in the United States, your file will be considered an overstay. This could cause serious problems if you attempt to enter the United States, including cancellation or denial of entry.
The visitor must prove that he/she left the United States within the time allowed for stay. If you lose or misplace your Form I-94/I94W departure record while you are in the United States or forget to turn it in, there are specific procedures you should follow.
The immigration officer keeps the top portion of the form upon arrival
The bottom is your departure record, which must be returned upon departure