Paychex, Inc. is an American company of human resources providers, payroll, and outsourcing services for small and medium-sized companies. With headquarters in Rochester, New York, the company has more than 100 offices serving nearly 670,000 payroll customers in the United States and Europe. in 2019, Paychex ranked 700th in fortune 500 for the largest companies in terms of revenue, and the company's revenue for fiscal year 2020 is expected to exceed $4.1 billion. Paychex was founded in 1971 by Tom Golisano, who started the company with only $3,000 and the process grew to include 18 franchises and partnerships, which were eventually merged into one private company in 1979. Paychex held an initial public offering in 1983 and started trading on the Nasdaq Index (PAYX). In December 2018, Paychex closed its acquisition of Oasis Outsourcing for $1.2 billion. At the time of the acquisition of Oasis, Paychex had 650,000 payroll customers and 14,500 employees. Oasis, a professional employers' organization (PEO), brought in 8,400 PEO customers, 1,100 employees and annual revenue of more than $9 billion in 2017. Following the acquisition of Oasis, Paychex provides outsourcing of human resources services to 1.4 million on-site employees.