Microsoft Corp. plans to lay off 2,850 employees, adding to previously announced job cuts as it retools its sales operations and dismantles its mobile phone hardware business.

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The software giant disclosed the latest cuts in a Thursday filing to the U.S. Securities and Exchange Commission.

Nine hundred of the layoffs in the global sales unit have already been completed, a spokesman said.

Those cuts are part of a restructuring announced earlier this month when former chief operating officer Kevin Turner departed Microsoft for hedge fund Citadel LLC's securities unit. His departure led Microsoft Chief Executive Satya Nadella to reorganize the sales group.

Microsoft disclosed the new leadership group as part of that reorganization, but it didn't publicly note the layoffs at the time.

The remaining 1,950 cuts, which Microsoft expects to complete by mid-2017, will include jobs in the sales organization and mobile phone division.

The latest cuts come on the heels of 1,850 layoffs in the phone unit, announced in May.

Write to Jay Greene at Jay.Greene@wsj.com