US Citizenship by descent

As I understand, the US has a five-year physical presence provision (with restrictions) in place to enable a foreign born US citizen to pass on citizenship to their child even though that child may him/herself may be born abroad.

The question is... In the absence of exit controls how does the US determine the length of time an individual has been in the country? I see that the US provision does not require residency, only physical presence. Even time spent on vacation can be counted toward the five-year requirement.

The reason I ask, is that the Canadian government just issued a reply to the House of Commons Standing Committee's recommendation to enact a residency provision for Canadians born abroad. The reply simply states that they cannot support a residency provision, as it would be impossible to enforce given the fact that Canada does not have exit controls.

It seems to me that the US is in the same boat and I'm curious as to how they handle the issue.

I suspect it's a "for the courts to decide" issue, but I suspect tax returns are a major way of determining it. US citizens have to file a 1040 every year or at least a Form 2555 if they're non-resident, even if they're under the reporting limit, so in theory it is possible to determine from tax records how long a person who claims to be a US citizen has been resident or not resident. Form 2555 specifically asks the question of how many days the person was resident in the US.

"US citizens have to file a 1040 every year or at least a Form 2555 if they're non-resident, even if they're under the reporting limit".

A little mixed-up there, steven. A USC need only to file 1040 if they meet the minimum income limit. They never have to file 2555, regardless of their income level, and quite simply can't file 2555 unless they have earned income, since it is the 'earned income exclusion'.

The manner of determining presence is the old-fashioned way (like in canada): sworn statement made under the penalty of deportation and loss of citizenship.