Reuters / Richard Brian
Ackman's hedge fund, Pershing Square, wants to replace five board members as well as the company's chief executive, according to a press release issued by ADP.
"Mr. Ackman requested that ADP extend the August 10 deadline for nomination of directors by 30 to 45 days and said he planned to nominate five directors, including himself, to ADP's 10-member Board," ADP said. "He also said CEO Carlos Rodriguez should be replaced."
ADP defended Rodriguez while taking a shot at Ackman. "Since Carlos Rodriguez became CEO nearly six years ago, ADP's total shareholder return of 202% is well in excess of the S&P 500 TSR of 128% - and is many multiples of Pershing's TSR of 29%," the release said.
The news comes about a week after Pershing Square announced it was taking a stake in the company. The size of the stake, about 8%, is mostly through derivatives, according to ADP.
This isn't the first time Ackman has owned a stake in ADP. He amassed a passive investment in company from 2009 to 2011, according to Bloomberg data.
Ackman is best known for his crusade against Herbalife. He has been an outspoken critic of the company, betting $1 billion against it. The trade has not gone his way.