Most business owners who sign PEO agreements spend a lot of time reviewing cost structures and service scope. Very few spend any time asking who is legally responsible for their employees’ benefits plans. That gap isn’t just an oversight — it’s a liability.
Here’s the scenario that tends to surface the problem: an employee’s health claim gets denied incorrectly, or a 401(k) plan has been quietly accumulating excessive fees for three years, or an ACA reporting error triggers a penalty notice. Suddenly, someone needs to answer the question: who was supposed to be watching this? In a PEO co-employment arrangement, that question is rarely as simple as it sounds.
This article is for business owners who already understand the basics of how PEOs work and want to go deeper on one specific dimension that often gets glossed over in the sales process: fiduciary oversight. We’ll break down how ERISA fiduciary responsibility actually allocates in a PEO relationship, where you’re protected, where you’re not, and what to scrutinize before you sign anything.
Why Fiduciary Responsibility Gets Complicated in a PEO Co-Employment Model
In a traditional employer setup, the answer is clean: you’re the plan sponsor, you’re the fiduciary, and you own the obligations that come with that. You select the health insurer, you oversee the 401(k) investment menu, and if something goes wrong with plan administration, it’s your problem to fix.
Co-employment changes that dynamic, but not in the tidy, all-or-nothing way that PEO marketing materials sometimes imply.
ERISA fiduciary duties don’t evaporate just because you’ve outsourced HR functions. Under ERISA Section 404, fiduciaries are held to duties of prudence, loyalty, diversification of plan assets, and strict adherence to plan documents. These obligations attach to whoever exercises discretionary authority or control over a plan or its assets. The question in a PEO arrangement is: which entity is exercising that discretion, and for which decisions? For a deeper dive into the financial dimensions of this issue, our analysis of fiduciary liability under the PEO model quantifies the actual exposure involved.
When a PEO sponsors its own master health or retirement plan, it typically steps into the plan sponsor role for those plans. That’s meaningful. It shifts a significant portion of fiduciary responsibility to the PEO entity. But “significant portion” is not the same as “all of it,” and the residual obligations that stay with you as the client company are often poorly understood.
There are also three distinct fiduciary roles under ERISA that matter here and often get conflated. A 3(16) plan administrator handles operational and administrative duties. A 3(21) investment advisor provides investment recommendations but shares fiduciary responsibility with you. A 3(38) investment manager takes full discretionary control over investment decisions, removing that specific liability from you entirely. Whether your PEO fills any of these roles — and which ones — varies dramatically across providers and isn’t always spelled out clearly in the service agreement.
The gray zone is real, and it’s where most of the risk lives. A PEO can be the plan sponsor of a master 401(k) plan while simultaneously disclaiming 3(38) investment manager status, leaving investment selection oversight in an ambiguous middle ground. That’s not a hypothetical edge case. It’s a common contractual structure that many business owners never read carefully enough to notice.
The Master Plan Structure and What It Actually Shifts
Most large PEOs — including well-known names like ADP TotalSource, Insperity, TriNet, and Justworks — sponsor their own master benefits plans. When you join one of these platforms, your employees are enrolled in the PEO’s plan rather than a plan you sponsor independently. This structure is one of the genuine advantages of a PEO relationship for smaller businesses.
As plan sponsor, the PEO assumes fiduciary duties for vendor selection, plan design, and benefits administration. For retirement plans, this typically includes oversight of the investment menu, plan document compliance, and coordination of required audits and filings. That’s fiduciary infrastructure that a 20-person company would struggle to build on its own, and it’s a real benefit.
The practical tradeoff is that you’re trusting the PEO’s fiduciary judgment with limited visibility into how they actually exercise it. You’re not sitting on their investment committee. You’re not reviewing their vendor evaluation process. You’re largely taking their word that they’re managing the plan prudently on your employees’ behalf.
Retirement plan structures add another layer of complexity. Some PEOs have adopted Pooled Employer Plans (PEPs), a structure formalized under the SECURE Act of 2019 and expanded under SECURE 2.0 in 2022. In a PEP, a Pooled Plan Provider (PPP) serves as the named fiduciary and plan administrator, taking on substantial fiduciary responsibility across all participating employers. This structure can further reduce your residual liability compared to older Multiple Employer Plan (MEP) models, but it also means your retirement plan governance is handled by an entity you may have even less direct visibility into.
Understanding which structure your PEO uses for retirement benefits isn’t just academic. It directly affects your residual fiduciary exposure and the questions you should be asking during due diligence. A PEO using a PEP structure with a qualified PPP is a materially different risk profile than one running a traditional MEP where fiduciary responsibility allocation is less clearly defined. The distinction between a CPEO and a standard PEO also matters here — our guide on CPEO vs PEO decision factors covers the regulatory differences that affect fiduciary structures.
For health benefits, the structure varies further. Some PEOs offer fully insured plans where the insurer carries the claims risk. Others use self-funded or level-funded arrangements where the plan itself bears claims exposure. In self-funded arrangements, fiduciary duties around claims processing and stop-loss coverage become more consequential, and the PEO’s oversight practices matter more.
Where Your Fiduciary Exposure Doesn’t Transfer
This is the section that tends to surprise people.
Even when a PEO is the named plan sponsor and has accepted significant fiduciary duties, you retain meaningful obligations as the client company. These don’t disappear because you signed a PEO service agreement, and they’re not always clearly enumerated in that agreement.
The duty to monitor: Under ERISA, selecting a service provider isn’t a one-time act. You have an ongoing obligation to periodically evaluate whether that provider is doing their job prudently. If your PEO’s 401(k) plan is consistently underperforming benchmarks, carrying excessive fees, or using investment options with undisclosed revenue sharing arrangements — and you never asked about any of it — that’s potentially your exposure too. The duty to monitor means you can’t simply outsource the question and forget it.
Employee communications and eligibility: Errors in communicating benefits options, eligibility windows, or plan changes to employees often remain the client company’s responsibility or create shared liability. If an employee misses an enrollment window because your internal HR team failed to communicate a deadline, the PEO’s plan sponsorship doesn’t insulate you from that.
COBRA administration: COBRA errors are a chronic source of liability in PEO relationships. The client company typically manages the initial qualifying event notification process, and failures at that step can create liability even when the PEO handles downstream COBRA administration.
ACA reporting accuracy: Affordable Care Act employer mandate reporting (Forms 1094-C and 1095-C) requires accurate data on employee hours, coverage offers, and affordability determinations. The underlying data comes from you. If it’s wrong, the penalties follow you, not the PEO.
Contribution timing: Ensuring that employee 401(k) contributions reach the plan on time is a fiduciary obligation that can create personal liability for business owners. Late remittances — even when caused by payroll processing delays — are a DOL enforcement priority. This doesn’t fully transfer to the PEO just because they run payroll. Understanding how to compare internal HR vs PEO expenses can help you evaluate whether the cost structure adequately accounts for these residual obligations.
The common thread across all of these is operational accountability. The PEO handles the infrastructure; you’re still responsible for the inputs, the communications, and the oversight of whether the infrastructure is actually working.
Red Flags Worth Scrutinizing Before You Commit
A PEO that takes fiduciary oversight seriously should be able to answer specific questions clearly and without hesitation. If you’re getting vague responses or redirects, that’s informative.
Investment policy statement: For retirement plans, ask whether the PEO has a documented investment policy statement (IPS) governing how the investment menu is selected, monitored, and replaced. An IPS is a basic indicator of whether fiduciary governance is formalized or ad hoc. Its absence is a red flag.
3(38) vs. 3(21) investment fiduciary: Ask directly whether the PEO uses an independent 3(38) investment manager for retirement plan assets. A 3(38) arrangement means a qualified third party has full discretionary control over investment decisions and accepts fiduciary liability for them. A 3(21) arrangement means they’re advising but you retain co-fiduciary responsibility. Many PEOs use 3(21) arrangements and market them in ways that obscure this distinction.
Independent plan audits: ERISA requires annual independent audits for plans with 100 or more participants. Ask who conducts the audit and whether it’s genuinely independent. A plan audited by a firm with other financial relationships to the PEO is not truly independent.
Fee transparency: Opacity around benefits fee structures is one of the clearest warning signs in a PEO relationship. Revenue sharing arrangements, per-participant charges, and insurance commissions embedded in benefits pricing can significantly inflate the true cost of a PEO relationship. A PEO acting in a fiduciary capacity should be able to articulate clearly how they’re compensated on benefits — including any indirect compensation. If they can’t or won’t, that tells you something. Comparing a PEO’s bundled approach against working with an independent advisor is worth exploring — our breakdown of PEO vs benefits broker models covers the fee transparency differences in detail.
Fiduciary liability insurance: Ask whether the PEO carries fiduciary liability insurance beyond the DOL’s minimum fidelity bond requirements. Under ERISA Section 412, plan fiduciaries are required to be bonded for at least 10% of plan assets handled, up to $500,000 (or $1 million for plans holding employer securities). That’s a floor, not a meaningful coverage level for a large plan. A PEO with substantial fiduciary exposure should carry dedicated fiduciary liability coverage above that minimum.
Contract language on fiduciary acceptance: Read the service agreement carefully for what the PEO explicitly accepts versus disclaims. Some PEOs use language that markets “fiduciary-grade” oversight while carefully avoiding any explicit acceptance of fiduciary status in the contract. If the contract doesn’t say they accept fiduciary responsibility for specific functions, assume they don’t.
Building Fiduciary Oversight Into Your PEO Evaluation
Most PEO comparisons focus on cost per employee, HR technology, and benefits breadth. Fiduciary oversight rarely makes the evaluation criteria list. It should.
Before signing — or renewing — request the following documents and evaluate them directly:
Form 5500 filings: The annual Form 5500 is filed with the DOL and is publicly available through the EFAST2 system. It discloses plan assets, participant counts, service providers, and fees. Reviewing a PEO’s Form 5500 for their master retirement plan gives you an unfiltered look at fee levels, service provider relationships, and whether audits were conducted. This is publicly available information that most business owners never look at.
408(b)(2) fee disclosures: For retirement plans, covered service providers are required to disclose their compensation under ERISA Section 408(b)(2). Request this disclosure and review it. If fees seem high or the disclosure is difficult to parse, that’s worth pressing on before you’re locked into a multi-year agreement. Building a PEO scenario analysis financial model can help you stress-test fee structures against different growth and claims scenarios.
Summary plan descriptions: Review the SPD for any benefits plan you’re considering. It documents plan rules, fiduciary roles, and claims procedures. Gaps or vague language in an SPD often reflect gaps in the underlying governance structure.
When comparing PEO providers side-by-side, treat fiduciary structure as a distinct evaluation dimension. Ask each provider the same questions about investment fiduciary roles, plan audit practices, and fee transparency. The variation in how different PEOs answer these questions is often more revealing than any marketing comparison sheet.
If you have 50 or more employees, or if your benefits program is complex, it’s worth having independent legal or benefits counsel review the fiduciary allocation language in a PEO service agreement before you sign. Our practical transition guide covers the due diligence steps you should complete before committing to any provider. The cost of that review is modest compared to the potential liability of signing something you didn’t fully understand.
The Bottom Line on Fiduciary Responsibility in a PEO Relationship
Fiduciary oversight in a PEO model isn’t binary. It’s a layered, shared structure where some duties transfer to the PEO, some stay with you, and some exist in a gray zone that depends on contract language, plan structure, and how operational decisions actually get made day to day.
The best PEO relationships are ones where this allocation is documented clearly, revisited periodically, and understood by both parties. Not assumed. Not buried in boilerplate. Actually understood.
When you’re evaluating PEO providers, fiduciary structure deserves the same scrutiny as cost and service scope. Ask about investment fiduciary roles. Request Form 5500 filings. Read the contract language on what the PEO accepts versus disclaims. Compare providers on these dimensions, not just on price per employee.
And if you’re approaching a renewal without having done this work yet — now is the time. Renewals are when you have the most leverage to ask hard questions and make changes if the answers aren’t satisfactory.
Don’t auto-renew. Make an informed, confident decision. PEO Metrics provides side-by-side provider comparisons that go beyond surface-level pricing to help you evaluate what you’re actually getting — including how different providers structure their fiduciary obligations. Before you sign another year, make sure you know exactly what you’re signing.
