ADP

ADP is a large payroll and human resources company that offers payroll processing, time and attendance tools, benefits administration, workers' compensation insurance, and professional employer organization services. Its small business payroll package covers businesses with 1 to 49 employees, while separate offerings serve midsized and large companies.

Small businesses can sign up online for payroll and get pricing through the website, and the company also lists a sales line. ADP's headquarters is at 1 ADP Blvd. in Roseland, New Jersey, and it serves clients across the United States and in many other countries.