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The FATCA - Foreign account tax compliance act - law has placed a heavy burden on U.S citizens with foreign financial accounts. The costs of complying and hiring the appropriate tax attorney to make sure the forms are properly filled out often costs more than the taxes that may, or may not, be owed. The law carries ridiculously harsh penalties for non-compliance or even for what may be honest errors. This is indeed a major reason why so many US expats are renouncing citizenship. It's become a practical necessity.

Lots of sad stories.

Under the law, if you stay outside the USA for a certain length of time, you do not pay USA tax,can not remember the amount of time right now, but you keep citizenship, just do not get to visit your homeland.