SEATTLE – Microsoft announced Tuesday that it plans to pay out as much as $75 billion of its cash hoard directly to shareholders through dividends and stock buybacks over the next four years.

The announcement ends speculation about what the giant software maker planned to do with the billions it has been sitting on.

The company said it will pay a one-time dividend of $3 a share and double its annual dividend to 32 cents a share. Microsoft, which has amassed at least $56 billion in cash, also plans to buy back up to $30 billion of the company’s stock over the next four years.

“We will continue to make major investments across all our businesses and maintain our position as a leading innovator in the industry, but we can now also provide up to $75 billion in total value to shareholders over the next four years,” chief executive Steve Ballmer said.

The one-time dividend is subject to shareholder approval of a plan intended to prevent employees who hold stock options or stock awards from being put at a disadvantage.

The concern is that the stock price will drop on the day of the payout, so the company wants permission to come up with a plan to make up for that loss. If that plan is approved, the special dividend would be paid out Dec. 2 to shareholders of record on Nov. 17.

Curt Anderson, Microsoft’s senior director of investor relations, said the company had not yet worked out details of how the massive cash buyback would work, or the exact timing.

Microsoft had previously been hesitant to spend the billions it has been amassing because of fears the money would be needed for legal disputes. But the company said Tuesday that the vast majority of its legal problems appear to be behind it.

Microsoft has settled many of its private antitrust claims, and it cleared its most significant U.S. legal hurdle when a federal appeals court unanimously approved an antitrust settlement the company negotiated with the Bush administration. It is still engaged in an antitrust battle with the European Union.

Microsoft announced plans for its cash reserves after the close of markets. In after-hours trading shares surged nearly 6 percent to $29.91.