A PEO is the "employer of record" in business model

In a co-employment contract, the PEO becomes the employer of record for tax and insurance purposes, filing paperwork under its own identification numbers. The client company continues to direct the employees’ day-to-day activities. PEOs charge a service fee for taking over the human resources and payroll functions of the client company: typically, this is from 3 to 15% of total payroll. This fee is in addition to the normal employee overhead costs, such as the employer's share of Medicare and unemployment insurance withholding. In addition, PEOs benefit from aggregation of employee headcount: by combining the employees from multiple clients, they qualify for lower premiums on health insurance plans.

A PEO generally generates some of its income through various methods of insurance, wage and tax arbitrage. In insurance products, a PEO will purchase workers' compensation, employment practices liability and employee benefits insurance at a given price. The PEO then adds a markup to the premium costs and bills that rate to the client company, which is still less than the company would pay on its own.

The value proposition to client companies is that the use of a PEO saves time and staff that would be used to prepare payroll and administer benefits plans, and may reduce legal liabilities or obligations to employees that it would otherwise have. The client company may also be able to offer a better overall package of benefits, and thus attract more skilled employees. The PEO model is therefore attractive to small and mid-sized businesses and associations, and PEO marketing is typically directed toward this segment.