Understanding the 80-120 Participant Rule

If your retirement plan’s participant count is near 100, a single number on your Form 5500 can have a big impact: whether you’re treated as a “small plan” or “large plan” filer. That classification can determine whether you need an independent plan audit and what schedules you must attach. The 80-120 participant rule is designed to reduce “flip-flopping” between small and large plan status from year to year—but it’s also commonly misunderstood.

Below is a practical guide to how the 80-120 participant rule works, how it ties to plan audits, and what HR teams and business owners should do when they’re close to the threshold.

What is the 80-120 participant rule?

The 80-120 participant rule is a Form 5500 filing rule that lets certain plans with between 80 and 120 participants at the beginning of the plan year continue filing in the same category (small or large) as they did the prior year.

In plain English: if you’re in the “border zone” around 100 participants, you may be allowed to keep filing as a small plan (or large plan) rather than switching back and forth each year.

This rule matters because, in general:

• Large plan filers typically must include an independent qualified public accountant (IQPA) audit report with the Form 5500 (unless an exemption applies).

• Small plan filers generally do not need an audit (again, unless special circumstances apply).

For background on the annual return itself, see our guide on what Form 5500 is and why it matters.

How the 80-120 rule affects whether a plan audit is required

Most plan sponsors first hear about the 80-120 participant rule when they’re trying to answer: “Do we need a retirement plan audit this year?”

Here’s the key point: the audit requirement is tied to your Form 5500 filing status (small vs. large), and that status is driven by participant count—with the 80-120 rule providing a filing-status “safe harbor” for plans in that range.

As a general framework:

• If you have 121+ participants at the beginning of the plan year, you generally file as a large plan and an audit is typically required.

• If you have 79 or fewer participants at the beginning of the plan year, you generally file as a small plan and an audit is typically not required.

• If you have 80–120 participants at the beginning of the plan year, you may continue filing as you did the prior year (small stays small, large stays large).

To go deeper on what an audit is and when it applies, read What Is a 401(k) Audit and When Do I Need One?. If you’re already facing an audit, our checklist-style resource, What Is Needed for a 401(k) Audit and Where Do I Find It?, can help you prepare.

If you need to engage an auditor, you can browse qualified firms here: 401(k) auditors, 403(b) auditors, defined benefit plan auditors, ESOP auditors, and health & welfare plan auditors (or see all auditors).

Who counts as a “participant” for the 80-120 rule?

This is where many Form 5500 mistakes happen. For the 80-120 participant rule, the participant count is generally based on the number of participants at the beginning of the plan year—and “participants” can include more than just employees actively deferring into the plan.

While details can vary by plan type and situation, participant counts commonly include:

• Active employees who are eligible to participate (even if they are not contributing)

• Employees with account balances (for example, terminated employees who left money in the plan)

• Retirees or beneficiaries receiving benefits (more common in pension/defined benefit contexts)

Practical takeaway: a plan can have 85 people contributing each pay period, but still have 110 participants for Form 5500 purposes because of former employees with balances.

For official guidance and instructions, refer to the government resources used to prepare filings, including the Department of Labor’s Form 5500 information page at DOL/EBSA Form 5500 resources and the Form 5500 materials available through EFAST2 (DOL).

Examples: how the 80-120 participant rule works in real life

Examples help because the rule is based on two things: (1) your beginning-of-year participant count and (2) what you filed last year.

1. Example A (staying small): Last year you filed as a small plan. This year you have 105 participants at the beginning of the year. Because you are between 80 and 120, you can typically continue filing as a small plan—often avoiding an audit requirement that would otherwise apply if you were forced into large plan status.

2. Example B (staying large): Last year you filed as a large plan and had an audit. This year you have 95 participants at the beginning of the year. Because you are between 80 and 120, you generally continue filing as a large plan (and typically continue the audit), rather than switching back to small plan filing.

3. Example C (breaking out of the range): Last year you filed as a small plan. This year you have 125 participants at the beginning of the year. You’re above 120, so you generally file as a large plan, which commonly triggers the audit requirement.

Common mistakes and compliance risks to avoid

Because the audit requirement can be expensive and time-consuming, it’s tempting to treat the participant count as a flexible number. That’s a risky approach. The participant count should be supportable from your records, and mistakes can lead to amended filings, DOL follow-up questions, and potential penalties.

Common pitfalls include:

• Counting only employees who contribute and forgetting eligible non-contributors or terminated participants with balances

• Using end-of-year headcount instead of beginning-of-year participants

• Assuming the 80-120 rule automatically eliminates the audit (it doesn’t; it preserves your filing status, and the audit requirement follows that status)

• Missing the Form 5500 deadline or filing without required attachments (including an audit report when applicable)

If you want to understand the real-world consequences, see The High Cost of Non-Compliance: Penalties for Late or Rejected Form 5500 Audits.

What plan sponsors should do when they’re near 100 participants

If your plan is trending toward (or hovering around) 100 participants, treat it as a planning issue—not a last-minute filing surprise. Here are practical steps that help:

1. Confirm your participant counting method early. Align payroll, recordkeeper, and TPA reporting so you can support the beginning-of-year count.

2. Forecast whether you’ll cross 120. If you expect 121+ at the start of next year, start budgeting and scheduling for an audit now.

3. Engage the right professionals. If an audit is likely, talk to experienced 401(k) auditors (or the right auditor type for your plan). If you need help evaluating providers and responsibilities, see How To Hire A Retirement Plan Advisor and our directory of 401(k) financial advisors.

4. Review related compliance items. For example, plans often need an ERISA fidelity bond. If you’re unsure, read What Is An ERISA Bond And How To Buy One? and compare options through our ERISA bond providers directory. When legal interpretation is needed, consider consulting ERISA attorneys.

Conclusion: use the 80-120 rule to plan ahead, not scramble later

The 80-120 participant rule is a helpful filing-status buffer for plans near the small/large plan line—but it’s not a loophole. The rule works only if your participant count is accurate and your Form 5500 filing status is consistent with the prior year.

If you’re approaching the threshold and want to avoid surprises, start by confirming your beginning-of-year participant count and mapping out whether an audit is likely. When you’re ready, explore qualified firms in our 401(k) auditors directory (or browse all auditors) and build an audit-ready process well before the Form 5500 deadline.