I need to end my visa waiver period when leaving States to Canada so that I don't exceed the period of 90 days. But form I-94 is no longer a physical card, it's only online.
How do I know or ensure that it will be terminated and will not continue counting the days once I leave to Canada?
I actually just found what I was looking for. According to US CBP at I94 FAQ:
Q: If I arrive via air but leave via land - thus I dont have paper form I-94 - how to report departure?
A: If you have a paper form I-94 and depart by land, you can turn the form into Canadian Border Services Agency (CBSA) upon entry into Canada or to CBP at the port of entry prior to entering Mexico.
If you received an electronic I-94 upon arrival by air or sea and depart via land, your departure may not be recorded accurately. A departure will be recorded if you depart via land and re-enter the United States prior to the expiration date stamped in your passport.
If you are not a resident of Canada or Mexico and you receive an electronic I-94 and depart via land, but do not re-enter the United States prior to the expiration date stamped on your passport, you may want to travel with evidence of your departure into Canada or Mexico. Evidence of departure can include, but is not limited to, entry stamps in a passport, transportation tickets, pay stubs and/or other receipts. A traveler can request an entry stamp from CBSA when entering Canada or from the InstitutoNacional de Migracion (INM) when entering Mexico.
Hope this helps everybody worried about it.
You don't need to worry, as it's all done electronically and automatically now, so you don't need to do anything yourself.
From the CBP page I-94 Goes Electronic:
Foreign visitors to the U.S. arriving via air or sea no longer need to complete paper Customs and Border Protection Form I-94 or I-94W. Those who need to prove their legal-visitor status—to employers, schools/universities or government agencies—can access their CBP arrival/departure record information online.
However if you arrived by land, you may still need to hand over your paper one if you received one:
Upon exiting the U.S., travelers previously issued a paper Form I-94 should surrender it to the commercial carrier or to CBP upon departure. Otherwise, CBP will record the departure electronically via manifest information provided by the carrier or by CBP.
If Arriving by land or sea and departing via air....
You will receive a paper I-94. However, when departing via air, your airline will ELECTRONICALLY record your departure. It might be a good idea to keep a boarding record and the paper I-94 in a safe place.
If Arriving by Air and departing via land or sea...
You will NOT receive a paper I-94. You will still need to prove to CBP you departed. So what you need to do on exit is ask CBSA or Mexican border authorities to stamp your passport, even if not normally done to prove your exit from the United States. This along with travel documentation will prove your exit from the US.
Also, CBP will advise you of your requirements on exit. They always ask how and when you'll be leaving and they would also be able to advise you of your legal requirements on entry.
