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How does the US know whether you have overstayed your tourist visa without having an exit stamp on your passport? How is it really calculated?

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in the old days they had no clue whatsoever. i'm pretty sure they do today - and I for one don't know how. perhaps just mining airline data? – Joe Blow Feb 23 at 17:00
This leaves out people crossing by foot to Mexico and like you mentioned, sailing off on a private boat etc., Since there are no exit checks, I'm just curious how they do it. – edocetirwi Feb 23 at 17:19
Are you talking about situation where someone overstayed in the past, but did leave, and is now re-entering? Do you want to know how the US officials at the new point of entry could tell that happened? – Colin McLarty Feb 23 at 17:31
@JoeBlow There've recently been some news articles about congressional testimony in which DHS officials have said that they don't in fact know how many have overstayed their visas. See for example…. – phoog Feb 23 at 17:48
@gerrit sometimes they'll ask questions they know the answer to to see how you react or whether you lie. – phoog Feb 24 at 17:03
up vote 17 down vote accepted

They don't. The US does not know how many people have overstayed their visas. This implies that in any individual case, the US can't be sure whether a person has complied with visa terms.

As others have mentioned, the US tracks exits by gathering data from the airlines and other carriers. However, because the US doesn't have exit controls, the system can easily be defeated. See, for example, the New York Times article U.S. Doesn’t Know How Many Foreign Visitors Overstay Visas.

A visitor to the US could fool the system by checking in for an international flight (for example, to London) and then swapping boarding passes with someone on a domestic flight (for example, to Chicago). The visitor then flies to Chicago, and the confederate flies to London. The US government believes that the vistor has left the country, but in fact, the visitor is in Chicago.

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Underestimating Uncle Sam a little too much? :P – Hanky Panky Feb 24 at 6:35
International flights usually have "passport and ticket" checks at the gate precisely to stop confederates sneaking on board. – jpatokal Feb 24 at 7:16
@HankyPanky I don't think so. The feds have failed to register several of my wife's exits, without any attempt at deceit. In the linked article, they about that the current system is full of holes. Why do you think I'm underestimating them? – phoog Feb 24 at 16:04
It was just a light hearted question referring to the phrase Uncle Sam knows everything :) – Hanky Panky Feb 24 at 16:32
@jpatokal I encounter such pass-and-ID checks routinely in other countries. In the US, not so much. See for example (start watching at 2:20 for the boarding pass scan). – phoog Feb 24 at 17:00

The US uses what they call a "biographical entry/exit system," which means that your biographical data (passport information) is tracked to determine when visitors enter and exit the country.

Entrance data is collected by immigration officers at points of entry, but as you note, the US has no exit controls, so where do they get exit data? Generally from airlines and the Canadian and Mexican authorities. The system is not perfect: there are some ways in which people leaving through Mexico aren't properly tracked, and sometimes there are data mismatches when people enter and exit on different passports.

Sometimes, if the system has gone wrong, the US will accuse you of overstaying when you haven't. In this case, you will want to carry proof that you did depart on time: plane tickets, passport stamps from other countries (you can always request a stamp from Canadian or Mexican officials), etc...

If you think that your arrival/departure records may be incorrect, you can check them online at

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You can literally walk or drive right into Mexico and nobody will say a word to you. If you want a Mexican entry stamp, you have to find an immigration officer, and that could be difficult. – Michael Hampton Feb 23 at 18:09
@MichealHampton, You can but you'll need to buy an FM-T, and get a stamp, if you are staying more than 72 hours or leaving the border zone for anywhere other than back to the US. They'll report this to the US. I think it is only for Mexican residents that a US exit might not be documented (which may be one source of overstay fuzziness). – Dennis Feb 24 at 22:47

The airlines will tell them.

Remember in the good old days of the green I-94W forms (this might actually still happen today for some countries?), they used to staple a part of the form in your passport? The check-in agent was then supposed to collect that part of the form, and it was supposed to be used by INS to check for overstayers (and more), though it probably wasn't always very accurate.

Nowadays this is just sent directly from the airlines computer systems. Whether it actually works is another matter.

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What about land border crossings? – 200_success Feb 24 at 1:04
I have filled the green I-94W forms. – gerrit Feb 24 at 11:14
@200_success at land borders, the traveler is supposed to give the form to a border officer. – phoog Feb 24 at 17:55

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