Co employment is the contractual arrangement at the heart of the PEO model: a client company and a professional employer organization allocate employer responsibilities between them under a client service agreement, so that both hold employer roles toward the same workers at the same time. NAPEO's definition is exactly that, a contractual allocation and division of employer responsibilities. The PEO typically takes the administrative employer functions, payroll, employment tax filing under its own EIN, benefits sponsorship and workers' compensation, while the client keeps the operational ones: hiring, firing, supervision and the daily direction of work. Understanding the split precisely matters, because both the fears and the sales claims around it tend to overstate what actually transfers.
What each party holds
Under a typical client service agreement, the PEO remits wages and withholdings for worksite employees, reports and deposits employment taxes with federal, state and local authorities, issues the W-2 for compensation paid under its EIN, sponsors benefit plans and provides workers' compensation coverage and claims management. The client retains ownership and control of the business itself: product, operations, marketing, and critically the workforce decisions, who is hired, how they perform, what they are paid and whether they stay. NAPEO's FAQ and ADP's explainer describe the same boundary from both sides of the market. Worksite safety and day-to-day compliance in how work is actually conducted also stay with the client, which is why a PEO relationship never substitutes for managing well.
Co employment is not joint employment, and control stays put
The most persistent fear about the arrangement, losing control of your company or your people, misreads the structure. ADP's treatment of the topic distinguishes co employment from joint employment: in joint employment two employers actually govern the same workers' terms and conditions, while in the PEO arrangement the client keeps sole oversight of its workforce and the PEO supplies infrastructure and administration. The employees work at your site, on your projects, under your managers; their W-2 carries the PEO's EIN because that is where payroll runs, not because the PEO directs them. The service agreement is where the real allocation lives, and it varies by provider, so the accurate answer to what does the PEO take over is always: read the CSA, clause by clause, before signing.
The liability nuance underneath the marketing
Co employment redistributes work; it redistributes federal tax liability only under conditions. IRS guidance on third-party payer arrangements holds that the client, as common law employer, generally remains responsible for employment taxes when a non-certified PEO handles them, and Treasury regulations can make both parties liable. The exception is the certified PEO: under Section 3511 a CPEO is solely liable for federal employment taxes on remuneration it pays to work site employees, with the relationship reported to the IRS. So the co employment structure itself is not what protects you on taxes; certification is, and it is verifiable on the IRS public listings. On everything else, employment claims, safety, wage-and-hour conduct, the allocation in the agreement plus how you actually manage decides exposure. This page describes the mechanism; the agreement controls, and it is not legal advice.
Questions people ask about co employment
Do my employees stop being my employees under co employment?
No. They work under your direction on your business; the PEO becomes an administrative employer for payroll, taxes and benefits under the service agreement. NAPEO and ADP both describe hiring, supervision and pay decisions as remaining with the client.
Whose name is on the W-2 in a co employment arrangement?
The PEO issues the W-2 for compensation it pays under its own EIN. That reflects where payroll and tax remittance run, not who directs the work.
Is co employment the same as joint employment?
No. Joint employment involves two employers actually governing the same workers. In the PEO arrangement the client keeps sole operational oversight while the PEO carries defined administrative responsibilities allocated in the client service agreement.
Does co employment shift employment tax liability to the PEO?
Only certification does that. A certified PEO is solely liable for federal employment taxes on wages it pays to work site employees; with a non-certified PEO the client generally remains responsible as common law employer, per IRS guidance.