Facebook to pay NO tax for 2012 and will even get tax refund of $429m despite $1BN profits

Article from last year Feb 15, 2012
Facebook to Pay Employees' $5 Billion Tax Bill - Technology and IT Jobs News and Advice

When the stock of Facebook employees gains liquidity with the company's IPO, Uncle Sam will be demanding $5 billion in taxes.
But luckily for those workers, Facebook will pick up the tab, according to a report in the Financial Times. Facebook isn't being completely unselfish; under U.S. tax rules, the company will be able to offset the tax bill against its profits and get a $500 million tax refund in 2013.

More info on the tax stuff: Facebook

So as I understand it, facebook paid its employees with equity, restricted stock units, when it was private. When facebook IPO, all the RSU become vested and the employees have to pay taxes on them as normal income. Facebook used its own money to pay the employees taxes, $5 billions of it, in 2012. That resulted in a net loss in 2012, so it was able to carry those losses forward and offset future profit against the losses in 2012.