Hewlett-Packard stunned Wall Street by alleging a massive accounting scandal at its British software unit Autonomy that will cost the company the majority of $8.8 billion in charges.

It was the latest in a string of reversals that have renewed questions about the basic competence of the storied company's board and senior managers.

HP said on Tuesday it discovered "serious accounting improprieties" and "a willful effort by Autonomy to mislead shareholders," after a whistleblower came forward following the ouster of Autonomy's then-chief executive, Mike Lynch, in May.