U.S. Customs & Border Protection (CBP) advises that if you returned home with your Form I-94 (white) or Form I-94W (green) Departure Record in your passport, it is possible that your departure was not recorded properly.
If you left the U.S. by a commercial air or sea carrier (airlines or cruise ships), your departure can be independently verified, and you don't need to do anything else, although holding on to your outbound boarding pass may expedite your reentry if you return to the United States.
If you departed by land, private vessel or private plane, you will need to correct the record. If you don't validate your timely departure from the U.S., or, if you cannot reasonably prove you departed within your approved time frame, the next time you apply for admission to the U.S., CBP may conclude you remained in the U.S. beyond your authorized stay and your visa may be subject to cancellation or you may be returned immediately to your foreign point of origin.
Under the Visa Waiver Program (VWP), visitors who remain beyond their permitted stay in the U.S. cannot reenter in the future without obtaining a visa from a U.S. Consulate. If you are a VWP visitor who traveled by land to either Canada or Mexico for an onward flight, it is especially important for you to register your timely departure if your green I-94W was not taken when you departed the U.S. If you fail to do so and you arrive at a U.S. port of entry seeking admission under the VWP without a visa, you may be immediately returned to a foreign point of origin. If you are a VWP visitor and you left the U.S. by an air or sea carrier, you don't need to worry.
If you did not turn in your I-94 Departure Record send it, along with any documentation proving you left the U. S. to: DHS - CBP SBU, 1084 South Laurel Road, London, KY 40744.
Don't mail your Form I-94 Departure Record or supporting information to any U.S. Consulate or Embassy or to any other address. This is the only location where CBP is able to make the corrections to its records to prevent future problems for you. This office does not answer correspondence, so confirmation that your record has been updated will not be verified.
To validate departure, CBP will consider a variety of information, such as: -Original boarding passes used to depart another country, such as Canada, if you flew home from there; -Photocopies of entry or departure stamps in your passport indicating entry to another country after departure from the U.S. (copy all passport pages that are not completely blank, including
the identification page with photograph); and -Photocopies of other supporting evidence, such as: dated pay slips or vouchers from your
employer to indicate you worked in another country after you left the U.S.; dated bank records
showing transactions indicating your presence in another country after departing the U. S.;
school records showing attendance at a school outside the U.S. demonstrating you were in
another country after you left the U.S.; and dated credit card receipts showing your name for
purchases made after you left the U.S. to show you were in another country after leaving the U.S.
Also include an explanation letter in English. Mail copies or original materials where possible. If you send original materials, you should retain a copy. CBP cannot return original materials after processing.
Carry your copies with you the next time you come to the United States in case the CBP Officer has any questions about your eligibility to enter. Carrying those materials with you will also allow your record to be corrected at the time of entry if, for some reason, the London, Kentucky office has not yet done so. If taking short trips (30 days or less) to Canada, Mexico, or the Caribbean Islands during the course of your visit to the U.S., hold onto your I-94 or I-94 (Wi)t; should only be turned in when you leave the U.S. to return home. Delays beyond the traveler's control, such as canceled or delayed flights, medical emergencies requiring a doctor's care, etc. are not considered unauthorized overstays, however, you will need to bring proof of the cause of your overstay next time you travel to the U.S. in order for it to be forgiven. For airline delays, ask the airline for a letter affirming the delay or a copy of your canceled boarding pass.