received a formal order of investigation from the
Securities and Exchange Commission
related to the company's stock option practices, according to an SEC filing.
UnitedHealth said Tuesday it will continue to cooperate with the SEC, which in April launched an informal inquiry into the matter.
UnitedHealth's former CEO, William McGuire, left the company after an independent probe found in October that many large options grants made were likely backdated to boost their value.
UnitedHealth has said it expects to recognize charges in financial statements for 1994 through Sept. 30, 2006.
Shares of UnitedHealth closed Tuesday down 22 cents, or 0.4%, to $53.23.