To renounce, you first have to meet several criteria:
• You must hold citizenship of another country, so you don’t become stateless.
• You have to be up-to-date with your U.S. tax filing, with the past five years submitted.
• You have to attend an exit interview at your nearest U.S. consulate or embassy.
• You have to pay a $2,350 renunciation fee.
• If you have financial assets worth over $2 million, you may have to pay a one-off exit tax calculated as a capital gains tax as if you sold all of your assets on the day you renounced.
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At least two of those points seem to be pretty prohibitive, if your goal is to avoid taxes on money already earned...