How does a country without exit immigration check know you have overstayed?

Question

Do countries without exit immigration check (like US or any other one) know you have overstayed when you're leaving the country?

And if not, does that mean that this overstayed person can easily come back to the same country later on a new valid visa or passport without being detected by the enter immigration and let in with no problem?

My friend, US citizen, just came back from the trip around eu (US-France-Germany-Ireland-London) and at no point, as he said, he saw exit immigration in any of those countries, including European ones.

Answer 1

Do countries without exit immigration check (like US or any other one) know you have overstayed when you're leaving the country?

Sometimes, but not always. For example, if you leave the US by air, the airline will provide your passport information to the US government, but not everyone leaves the US by air. If you leave by land to Canada, the Canadian government will share information about people entering with the US. But, as of 2023, the Mexican government does not share information about people entering with the US. (See this Congressional Research Service report, page 11 (14th page of the PDF).) Therefore, if the US government does not have a record of someone leaving, it may not be able to distinguish between someone who is still in the US, and someone who has left by land to Mexico.

And if not, does that mean that this overstayed person can easily come back to the same country later on a new valid visa or passport without being detected by the enter immigration and let in with no problem?

No. If, upon the next visa application or entry, the officer sees that the person had an entry without a corresponding exit the last time, the officer will probably place the burden upon the person to prove that they left on time (e.g. with an entry stamp to another country, or other evidence that places the person in another country on a certain date).

Answer 2

While there is no check, there is information. Nowadays this is all electronic, but there were other means before that.

For instance, in the US, visitors used to have a part of their I-94 stapled into their passport when they entered the country. On exit, the check-in agent would take it from the passport, and all collected I-94s would be send to the relevant agency. Of course it was extremely inefficient (I have no idea what actual processing was done with those forms, honestly).

Nowadays this is mostly all electronic. Airlines provide manifests (lists of passengers) with more or less information to the relevant authorities, which try to match them to the relevant record (which is straightforward in most cases even with very minimal info, but can be more difficult in special cases like people having multiple passports, possibly with different names, or extremely common names...).

Visitors to the US can see the result by checking their own I-94 online after leaving the US: the exit will (should?) have been recorded even though they never met a CBP agent on their way out.

For a long time there were a number of "holes" in the system, for instance:

• In the UK only airlines provided the info (and I think not even all of them). Train (Eurostar), ferry and bus companies didn't. This has been addressed since.

• There was a hole for people exiting the UK via Ireland. Since the UK and Ireland are part of the CTA (Common Travel Area), exits to Ireland were not recorded, and either Ireland did not record exists or did not report them to the UK, don't remember which. I think this has been addressed as well.

Also, note that some of the flights in your friend's itinerary (FR-DE and IE-UK) are internal flights/trips (Schengen for the former, CTA for the latter), and don't necessarily have border control at either end anyway.

However there IS exit passport control out of Schengen, so your friend did nearly certainly meet a border agent when they flew from Germany to Ireland. They should have a matching stamp in their passport. If they don't, they should keep evidence that they actually left the Schengen area on that date (boarding passes, hotel receipts in other countries), because those stamps are currently the only record of Schengen entries and exits.

US-France-Germany-Ireland-London-US:

• US exit: no check
• FR entry: check
• FR-DE: internal, no checks other than ID
• DE exit: check
• IE entry: check
• IE-UK: internal, no checks other than ID
• UK exit: no check

Answer 3

In most cases, like in the US or the UK, the airline will report your travel to the authorities themselves (through Advance Passenger Information or API)

I don't know how they could have seen no control in either Germany or Ireland, as, to exit the Schengen Area you must pass border control, and to enter Ireland you must pass entry control

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However, those border controls can be achieved using Automatic Passport Control, which some nationalities are eligible to use.

Because this is why I assume happened.

For Germany, EU/EEA/CH citizens + Residents of Germany + pre-registered US/HKSAR/TW/ROK citizens are eligible. But, until the Entry Exit System (EES) is implemented, a stamp is still to be applied.

For Ireland, EU/EEA/CH + US/CA/AUS/NZ/JP citizens (unless transiting to the UK) are eligible.