Facebook co-founder, Eduardo Saverin, has renounced his U.S. citizenship, according to an Internal Revenue Service report, just days before the company's record initial public offering.
The news, first published by Bloomberg on Friday, was based on an IRS notice late in April, which names individuals "who have chosen to expatriate."
Facebook plans to raise as much as $10.6 billion in an IPO that values the company at as much as $96 billion.
The offering could leave Saverin - who once owned 5 percent of the company - with a hefty capital-gains tax bill.
Saverin has sold enough of his Facebook stake that he doesn't appear in IPO filing documents that list shareholders who own 5 percent or more of the company, though his holdings are still believed to be substantial.
He now lives in the Asian city-state of Singapore, which has no capital-gains tax. That compares with a minimum 15 percent rate for long-term capital gains in the United States for people in higher income brackets.
The Brazil-born Saverin was educated in the U.S. at Harvard, where he co-founded Facebook with Mark Zuckerberg and others.
Renouncing citizenship is a complicated and lengthy affair involving a signed oath and an appearance before a U.S. diplomatic official, according to the U.S. State Department's Web site.
Giving up citizenship is an irrevocable act, the State Department says.