Microsoft Corp Chief Executive Steve Ballmer failed to clinch his maximum bonus for the second year running due to the company's slow progress in mobile phones and adapting to the tablet computer revolution.

Ballmer, 55, got a bonus of $682,500 for the latest fiscal year, matching his annual salary, according to a filing with securities regulators on Monday. Under his bonus scheme, he was eligible to receive between zero and double his salary.

Last year, Ballmer also received a bonus equaling his salary, and was faulted for the failure of the Kin phone and keeping up with new forms of computing.

Microsoft's latest filing said Ballmer's performance review for fiscal 2011 -- which ended June 30 -- took into account lower than expected sales of Windows Phone 7 software and the need for further progress in new form factors, a reference to Microsoft's inability to counter runaway sales of Apple Inc's iPad.

It also pointed to a 2 percent dip in sales at its key Windows unit, which was in line with global PC sales, but also shows that Apple's tablet is starting to eat away at the core computer market.

Microsoft is not expected to enter the tablet market in earnest until next year, when it releases its next operating system, code-named Windows 8.

In Ballmer's favor, the company's compensation committee recognized his success in launching the Kinect hands-free gaming system for Xbox and the online Office 365 product, while building up the Azure cloud computing platform and Bing search engine.

It also mentioned his work toward the purchase of online chat company Skype, which has not yet been completed, and partnerships with Facebook and phone maker Nokia.

(Reporting by Bill Rigby; Editing by Gary Hill)