A NONIMMIGRANT must turn in his Arrival-Departure Record (Form I-94) prior to departing from the US in order to prove that he departed within the time frame given to him at the time of arrival.

If the nonimmigrant is departing by air or sea, he must turn in his Form I-94 to airline personnel or shipping line personnel prior to departure.
If the nonimmigrant is departing by land and will not be returning to the US within 30 days, he must turn in his Form I-94 to the Canadian or Mexican authorities upon departure from the US.

The Form I-94 is the white document that a nonimmigrant receives from a US Customs and Border Protection (CBP) officer upon arrival at a US port of entry. It shows the date he arrived in the US and the "Admitted Until" date, the date when his authorized period of stay expires, and class of admission.

The failure of a nonimmigrant to turn in his Form I-94 at the end of his visit could result to the cancellation of his nonimmigrant visa and/or refusal by the CBP to allow him to reenter the US.

According to the latest memo issued by the CBP regarding this issue, there are ways to validate your timely departure from the US even if you failed to turn in your Form I-94 when you left the US.

If you departed by a commercial air or sea carrier (airlines or cruise ships), then no further action is necessary since your departure from the US can be independently verified. It is advisable, however, to hold on to your outbound (from the US) boarding pass, if you still have it, since it can help expedite your reentry next time you come back to the US.

If you departed, however, by land, private vessel or private plane, you will need to take steps to correct the record. You must send your Form I-94, along with any documentation that proves you left the US to:
DHS - CBP SBU
1084 South Laurel Road
London, KY 40744

Do not mail your Form I-94 or supporting information to any US Consulate or Embassy, to any other CBP office in the US, or to any address other than the one above.

To validate departure, CBP will consider a variety of information, including but not limited to:
1.Original boarding passes you used to depart another country, such as Canada, if you flew home from there;
2.Photocopies of entry or departure stamps in your passport indicating entry to another country after you departed the US (you should copy all passport pages that are not completely blank, and include the biographical page containing your photograph); and
3.Photocopies of other supporting evidence, such as:
Dated pay slips or vouchers from your employer to indicate you worked in another country after you departed the US,
Dated bank records showing transactions to indicate you were in another country after you left the US,
School records showing attendance at a school outside the US to indicate you were in another country after you left the US, and
Dated credit card receipts, showing your name, but, the credit card number deleted, for purchases made after you left the US to indicate you were in another country after leaving the US

You must keep a copy of what you send to DHS-CBP and carry it with you the next time you come to the US 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.