TPA vs. 3(16) Plan Administrator: What's the Difference and What Do They Cost?

If you sponsor a 401(k) plan, you almost certainly work with a third-party administrator (TPA). But increasingly, plan sponsors are being offered an upgrade: a 3(16) fiduciary plan administrator. Both handle the day-to-day mechanics of plan compliance, but only one accepts legal responsibility for the work. The difference matters — in both liability and cost.

What Is a Traditional TPA?

A traditional third-party administrator (TPA) is a service provider hired to handle the operational and compliance tasks associated with running a 401(k) plan. This typically includes:

• Preparing and filing the Form 5500 annual return
• Performing nondiscrimination testing (ADP, ACP, and top-heavy tests)
• Calculating employer contribution allocations
• Processing loans and hardship withdrawals per plan terms
• Preparing plan amendments for regulatory and design changes
• Coordinating with the recordkeeper on participant eligibility and vesting

Despite the depth of these services, a traditional TPA operates in a ministerial capacity. They carry out the plan sponsor's instructions — they do not make discretionary decisions. Under ERISA, this means a traditional TPA is not a fiduciary. If a test is run incorrectly, a distribution is processed out of compliance, or a filing deadline is missed, the legal exposure rests with the plan sponsor, not the TPA. The TPA may face a breach-of-contract claim, but ERISA's personal liability provisions do not apply to them.

What Is a 3(16) Fiduciary Plan Administrator?

The designation “3(16)” comes from ERISA Section 3(16)(A), which defines the plan administrator — the party legally responsible for running the plan in compliance with ERISA and the plan document. By default, the plan sponsor is the 3(16) plan administrator. But ERISA explicitly permits the sponsor to appoint another entity to serve in this role.

When a service provider accepts a 3(16) appointment, they are accepting fiduciary status. That means they are personally liable under ERISA if they breach their duties. Practically, this shifts accountability for administrative compliance from your organization to theirs. A full 3(16) engagement includes the provider signing the Form 5500 as Plan Administrator — a key indicator of genuine acceptance of the role. If your plan sponsor is still signing the Form 5500, you are likely receiving a limited “3(16) Lite” service, not a full fiduciary delegation.

Common services included in a full 3(16) engagement:

• All traditional TPA services (testing, Form 5500, distributions, amendments)
• Signing the Form 5500 as plan administrator — legally binding acceptance of the role
• Making discretionary decisions on eligibility, vesting, and distribution approvals
• Correcting plan document failures and operational errors under IRS correction programs
• Monitoring for regulatory changes and proactively amending the plan as required
• Managing payroll integration — reviewing contribution data from the employer and reconciling it against plan records

A Critical Distinction: Retained Monitoring Duty

Delegating to a 3(16) administrator significantly reduces a plan sponsor's administrative burden — but it does not eliminate fiduciary responsibility entirely. ERISA is clear: a plan sponsor can never fully abdicate their fiduciary duty. The duty to prudently select and monitor the 3(16) provider remains with the plan sponsor at all times.

This means the appointment itself must be prudent and documented, and the plan sponsor must conduct regular reviews of the 3(16)'s performance. The risk shifts — but it does not disappear.

Side-by-Side Comparison

What Does Each Service Cost?

TPA fees vary by plan size, complexity, and the number of participants. For most small to mid-size plans:

• Traditional TPA fees typically range from $1,500 to $10,000 per year, with many plans in the $2,000–$5,000 range. Fees are typically structured as a base fee plus a per-participant charge.
• 3(16) fiduciary administration fees typically command a 30% to 50% premium over standard TPA fees — reflecting the additional liability, discretionary services, and depth of oversight. Expect $3,000–$20,000 per year for most plans, depending on size and complexity.

Under ERISA Section 408(b)(2), your TPA or 3(16) administrator is required to provide a written fee disclosure identifying all compensation — both direct fees and any indirect compensation (such as revenue sharing payments from the recordkeeper). Always request and review the 408(b)(2) disclosure from your administrator and check whether they receive indirect compensation from your recordkeeper or investment providers in addition to the fees you pay directly.

Why Are Plans Choosing 3(16) More Often?

SECURE Act 2.0 (2022) introduced regulatory requirements that take full effect in 2026 — including mandatory automatic enrollment for new plans and Roth catch-up contribution requirements for employees earning $145,000 or more. The increased complexity of plan administration under these rules is making the 3(16) model more attractive for sponsors who want to reduce their own compliance burden.

Plan sponsors commonly cite three drivers:

• Risk reduction: When the 3(16) is a fiduciary, they are accountable for administrative errors under ERISA. For plan sponsors without dedicated HR or benefits staff, this is a meaningful shift in exposure.
• Bandwidth: Day-to-day compliance decisions — eligibility determinations, distribution approvals, correction filings — are delegated to a specialist. HR teams are freed from recurring plan administration tasks.
• Regulatory complexity: With SECURE 2.0 compliance deadlines arriving and IRS guidance still evolving, sponsors prefer to have a named fiduciary responsible for keeping the plan current.

Prudent Monitoring: Your Retained Duty

Even with a full 3(16) appointment in place, the plan sponsor retains the fiduciary duty to prudently select and monitor the administrator. This monitoring duty should be conducted at least annually. Questions to ask during your annual 3(16) review:

• Did the administrator meet all Form 5500 filing deadlines, including any required extensions?
• Were nondiscrimination tests completed on time and with no unresolved failures?
• Were required plan amendments (for SECURE 2.0, IRS guidance, etc.) drafted and executed promptly?
• Were any operational errors identified? How were they corrected, and under which IRS or DOL correction program?
• Is the administrator's 408(b)(2) disclosure current? Does it include all direct fees and any indirect compensation received from the recordkeeper or fund companies?
• Is the administrator financially stable? Do they carry fiduciary liability insurance, and at what coverage limit?

Document the results of this review in your fiduciary file each year. An undocumented delegation is not a defense — the evidence of your monitoring process is what demonstrates prudence.

How to Decide Which One Your Plan Needs

For most plans under $5 million in assets with a dedicated HR or benefits manager who reviews and approves every administrative decision, a traditional TPA is appropriate and cost-effective.

A 3(16) fiduciary administrator becomes worth the premium when:

• Your HR team lacks bandwidth to review and approve administrative decisions in real time
• Your plan has had prior operational failures or correction filings
• Your plan is growing quickly and administration complexity is increasing (more participants, multiple eligibility classes, employer matching formulas)
• Your company has been involved in or is concerned about ERISA litigation exposure
• Your plan sponsor board or investment committee wants documented risk transfer for administrative compliance

Whatever your choice, the fees paid to your TPA or 3(16) administrator must be benchmarked as part of your ERISA 408(b)(2) review process. Document that the fees are reasonable in relation to the services provided — and retain that documentation in your fiduciary file.