The complaint alleges that AES made false/misleading statements or failed to disclose that:

• The company was employing improper accounting practices, particularly with respect to its method for recognising revenue for its emission control business segment contracts
• The company was experiencing increased operating losses, primarily driven by a reduction of revenues and margins for its emission control segment with a corresponding increase in backlog
• The improper accounting practices would require the company to restate its reported financial statements; and
• As a result of the above, the company's financial statements were materially false and misleading at all relevant times.

In a Securities and Exchange Commission Form 8-K filing on March 13 this year, AES announced: "The company is currently reviewing its accounting practices, particularly its methods of recognising revenue for its emission control business segment contracts.

“The company expects the result of this review will likely result in increased operating losses, primarily driven by a reduction of revenues and margins for its emission control segment with a corresponding increase in backlog for the same period."

Following the news, company shares fell from $US54.23 ($A58.50) to $50.90 on the same day.

Plaintiffs are seeking to recover damages on behalf of all class members who invested in Advanced Emissions securities during the class period.