From Good Morning Silicon Valley.

Microsoft CEO Steve Ballmer last week sold 49.3 million shares in the company worth $1.3 billion, according to an SEC filing. The shares Ballmer sold amount to 12 percent of his stake in the world’s largest software maker, and still leaves him with a 4.2 percent stake, according to Reuters.

The timing, coinciding with high-profile product releases of the Kinect and Windows Phone 7 — which are now on sale in the United States — might be curious. But in a statement on Microsoft’s website, Ballmer cites tax planning and financial diversification as reasons for his first stock sale in seven years, and says he plans to sell up to 75 million shares by the end of the year. “Even though this is a personal financial matter, I want to be clear about this to avoid any confusion. I am excited about our new products and the potential for our technology to change people’s lives, and I remain fully committed to Microsoft and its success,” Ballmer said.

Tech industry veteran Don Dodge estimates that the move will save the outspoken CEO $100 million in capital gains taxes before they rise next year.

As the man said, a billion here and a billion there and pretty soon you’re into some serious money.