Paychex Inc. (NASD: PAYX) today completed its acquisition of Oasis Outsourcing Acquisition Corp., one of the largest professional employer organizations in the US. The purchase price was $1.2 billion, subject to customary closing adjustments.

Paychex and Oasis will continue operating as separate entities.

Rochester, NY-based Paychex announced the transaction last month. It will now count more than 1.4 million worksite employees through its HR outsourcing services.

Oasis, headquartered in West Palm Beach, Fla., counts more than 8,400 clients nationwide and provides HR solutions, employee benefits, payroll administration and risk management services.