As I understand it, US citizens must file a US federal tax return on all of their worldwide income, even if they are currently not residents in the US. Are there exceptions to this?
Here is the case someone asked me about today. A citizen of Brazil, who was born in Brazil and lived there for their entire lives, obtains US citizenship. The person might have done this in order to have a US passport, or it might have just been a "vanity" issue to have dual citizenship. Do such individuals now have an obligation to file a US tax return on their Brazilian income? Obviously they get a credit for foreign taxes paid. I'm not asking about the mechanics of the return, but rather just when there is an obligation to pay US tax and file.
Assuming such an individual later realizes their mistake and wants to back out, are they subject to all of the stiff penalties that the IRS has set up for US citizens who renounce citizenship?