Mark Zuckerberg winner for CEO of the Year at the 6th Annual Crunchies Awards at Davies Symphony Hall on January 31, 2013 in San Francisco, California. (Photo by Steve Jennings/Getty Images for The Crunchies)
UNDATED (CNN) -- It might be time for Mark Zuckerberg to un-friend Uncle Sam.
The Facebook CEO is expected to owe the IRS more than a billion dollars in taxes for 2012.
The momentous bill stems from his decision to exercise a stock option and buy more than 60 million Facebook shares when the site went public.
Even though we don't know exactly what he'll owe, it is known that the I-R-S will treat his stock options as income, which translates to roughly two billion dollars.
And since Zuckerberg's tax rate is close to 50 percent, well, you can do the math.
Zuckerberg knew the giant tax bill was coming, so he sold more than 30 million shares during Facebook's IPO to cover it, according to a Facebook regulatory filing.