When a US citizen relinquishes citizenship or a long-term US resident (green card holder) leaves the US, new rules in effect since June, 2008 can apply to treat the expatriate as if he or she sold all of his or her assets (worldwide) as of the date of expatriation, triggering an immediate income tax on all appreciated assets. This rule is intended to prevent expatriates from moving their assets offshore without paying tax, and can have significant adverse tax consequences.