ADP (NASD: ADP) investor Pershing Square Capital Management is seeking effective control of ADP through five board seats at ADP’s 2017 annual meeting as well as the replacement of CEO Carlos Rodriguez. The Roseland, NJ-based professional employer organization provides other services, including paycheck processing.

Pershing Square beneficially owns 8% of ADP, largely in derivatives, making it Pershing Square’s largest investment. It first contacted ADP on Aug. 1, and met in-person with the firm Aug. 3, requesting ADP extend the Aug. 10 deadline for nomination of directors by 30 to 45 days. Pershing Square plans to nominate five directors, including founder and CEO William Ackman, to ADP’s 10-member board.

“ADP is open to constructive input from our shareholders, and our board respects the right of shareholders to nominate directors,” ADP said in a statement. “However, ADP has a clearly defined board nomination process, and the 2017 deadline for director nominations has been public for nearly a year. The board has unanimously determined that it is not in the best interests of ADP or its other shareholders to accede to Pershing Square's last-minute request for an extension.”

“We were disappointed to learn from an ADP press release that the company has denied our request for an extension that could have facilitated constructive discussions,” Pershing Square said. “Accordingly, Pershing Square will nominate a minority slate to the board.”