Mark Zuckerberg, chief executive officer and founder of Facebook Inc., speaks to attendees during an event at the company's headquarters in Menlo Park, California on Thursday, April 4, 2014. Photographer: David Paul Morris/Bloomberg News *** Local Caption *** Mark Zuckerberg

San Francisco - Facebook chief executive Mark Zuckerberg reaped a $3.3 billion (R35bn) gain last year by exercising stock options in the social networking company he founded.

The windfall saddled Zuckerberg with a huge tax bill, even though he limited his Facebook salary to just $1, according to regulatory documents filed on Monday.

It is the second consecutive year that Zuckerberg has realised a massive gain on the holding that he has accumulated in Facebook since he started the company in 2004 while at Harvard University. In 2012, Zuckerberg made $2.3bn from his stock options.

Zuckerberg, 29, has exhausted his supply of stock options after exercising 60 million of them last year at a price of 6c a share. He then sold 41.35 million shares for $55.05 each in December, primarily to pay for his tax bill on the gains.

Zuckerberg and his wife, Priscilla Chan, donated 18 million Facebook shares to a non-profit organisation in December. The gift, worth nearly $1bn at the time, put the couple at the top of an annual list of the most generous Americans.

Even after selling and donating so much stock, Zuckerberg still owns 426.3 million Facebook shares, now worth $25.7bn.

The stock has more than doubled in value during the past year as Zuckerberg fulfilled his promise to sell more adverts on smartphones and tablets. The company now gets more than half its advertising revenue from mobile devices, up from 23 percent at the beginning of last year.

Besides an annual salary of $1 last year, Zuckerberg received perks valued at $653 164. All but $3 000 of that amount went toward his bills for personal travel on chartered jets.

Excluding stock option gains, Zuckerberg’s total compensation last year plunged 67 percent from nearly $2 million in 2012.

Total compensation was calculated by adding salary, bonuses, perks, above-market interest that the company pays on deferred compensation and the estimated value of stock and stock options awarded during the year.

The formula does not count changes in the present value of pensions, a benefit that Facebook and most other technology companies do not provide. - Sapa-AP