Bill Ackman is buying up shares in a company that might manage your firm’s payroll

Billionaire hedge fund manager Bill Ackman is loading up on shares of Advanced Data Processing , a New Jersey-based provider of payroll and benefits services.

The Pershing Square Capital Management CEO's initial purchases of ADP stock are already completed, but he may buy additional shares through new funds that he's launching, according to a Bloomberg News report . It's not yet known how large Pershing's stake in ADP is, and it's unclear at this point whether Ackman will fight for changes in the company's operations, as he has in past investments.