Do Solo 401(k) Plans Need an Audit?
Most Solo 401(k) plans do not need an audit—but there are important conditions. Here’s what the DOL audit rules say, how “participant” is counted, and what Solo K owners should still file and monitor.
If you sponsor a Solo 401(k) (also called an “individual 401(k)” or “Solo K”), you’re probably hoping it stays simple—fewer people, fewer headaches, and ideally fewer compliance requirements. The good news: most Solo 401(k) plans do not need an annual audit. The important part is understanding why that’s true and when it can change.
Do Solo 401(k) plans need an audit?
Usually, no—Solo 401(k) plans generally do not need an annual ERISA audit. That’s because most Solo 401(k) plans are not subject to ERISA when they only cover the owner(s) and spouse(s), and the ERISA annual audit requirement is tied to ERISA coverage.
However, yes—an audit can be required if your plan stops being “solo” (for example, you hire employees who become eligible and participate). In that case, the plan may become ERISA-covered and may eventually be subject to the audit rules that apply to other employer-sponsored plans.
What the DOL audit rules actually apply to (and why Solo K is different)
No—DOL’s annual audit rules don’t typically apply to owner-only plans. The Department of Labor (DOL) audit requirement is part of the annual reporting rules for ERISA-covered plans, generally tied to the Form 5500 filing and the “large plan” audit requirement.
In plain English:
ERISA-covered plans may need an independent qualified public accountant (IQPA) audit when they are considered a “large plan” for Form 5500 purposes.
Owner-only plans (covering only owners and their spouses) are generally not ERISA plans, so the DOL audit requirement usually doesn’t attach.
For the underlying government framework, you can review the DOL’s ERISA overview and reporting/audit concepts here: DOL overview of ERISA and the DOL/EBSA Form 5500 information here: EBSA Form 5500 fact sheet.
Is there an asset threshold for Solo 401(k) audits?
No—there isn’t a special “Solo 401(k) audit threshold” based on assets. You’re not wrong to think “under a certain amount” matters, but that concept applies more directly to Form 5500 filing for Solo 401(k)s, not to audits.
Here’s the common rule business owners run into:
Yes—Solo 401(k) plans generally must file Form 5500-EZ once plan assets exceed $250,000 at the end of the plan year (or when the plan terminates).
No—filing Form 5500-EZ does not automatically mean you need an audit. The audit requirement is generally associated with ERISA-covered plans filing the “long” Form 5500 as a large plan.
If you want a practical refresher on the annual filing itself, see our guide: what Form 5500 is and why it matters. And if you’re concerned about filing mistakes or delays, read: penalties for late or rejected Form 5500 filings and audit issues.
For the government source on Form 5500-EZ and owner-only plan reporting, the IRS maintains resources here: IRS retirement plan reporting and disclosure requirements.
Do family-member-only participants keep it “solo”?
It depends—sometimes yes, sometimes no. Your instinct that “family members only” can keep things simpler is partly right, but it comes down to whether those individuals are owners (and/or spouses of owners) versus common-law employees.
Yes—if the only participants are the business owner(s) and their spouse(s), the plan is generally treated as an owner-only plan and typically not ERISA-covered.
No—if you employ family members who are not owners (or not spouses of owners) and they become eligible, you may have moved out of “Solo 401(k)” territory. At that point, ERISA may apply and your plan could eventually face the same audit framework as other employer plans.
Because eligibility rules can be tricky (especially with part-time work, controlled groups, and family businesses), it can be worth getting a second set of eyes from a professional. If you’re evaluating help, see: how to hire a retirement plan advisor or browse 401(k) financial advisors. For legal interpretation and risk-sensitive questions, consider speaking with an ERISA attorney.
Do Solo 401(k) plans need an ERISA bond?
Usually, no—owner-only Solo 401(k) plans generally do not need an ERISA bond. ERISA bonding requirements typically apply to ERISA-covered plans and protect the plan from fraud or dishonesty by people handling plan funds.
Yes—if your plan becomes ERISA-covered, bonding requirements may apply. If you’re unsure what bonding is or how to purchase it when required, see our explainer: what an ERISA bond is and how to buy one. You can also explore options through our ERISA bond providers directory.
For the DOL’s bonding rules overview, see: EBSA fact sheet on fidelity bonding.
When a “Solo 401(k)” can become an audit situation
No—simply growing plan assets doesn’t usually create an audit requirement for a true owner-only plan. The more common trigger is adding eligible non-owner employees and becoming ERISA-covered.
Here are practical scenarios that can change your compliance profile:
You hire employees who meet eligibility requirements (based on your plan document) and they participate.
Your business structure changes (for example, adding partners or entities that create a controlled group) that affects who must be covered.
You merge, acquire, or spin off a business and employee benefit coverage changes.
If you think you’re approaching “non-solo” status, it’s smart to plan ahead. If an audit ever becomes required, you’ll want to understand the process and timelines. Start here: what a 401(k) audit is and when you need one and what is needed for a 401(k) audit and where to find it. You can also browse qualified firms in our 401(k) auditors directory (or see all auditors if your plan type differs).
Quick compliance checklist for Solo 401(k) owners
No—you probably don’t need an audit, but you still need good habits. Use this short checklist to stay ahead of common issues:
Confirm your participant status annually: Are you still owner-only (owners/spouses only), or do you have eligible employees?
Track plan assets at year-end: If you exceed key thresholds, you may have a Form 5500-EZ filing obligation.
Keep clean records: contributions by source (employee deferrals vs. employer contributions), loan paperwork (if any), and investment statements.
Review your plan document: especially eligibility, entry dates, and compensation definitions.
Conclusion: Most Solo 401(k)s don’t need audits—but confirm you’re truly “solo”
No—most Solo 401(k) plans do not need an audit because they generally aren’t ERISA-covered when they only cover the owner(s) and spouse(s). Yes—your obligations can change if you add eligible employees or otherwise move into ERISA territory.
If you’re uncertain whether your plan is still owner-only, or you’re hiring and want to avoid accidental compliance problems, consider getting guidance from a 401(k) financial advisor or an ERISA attorney. And if you ever do cross into audit-required territory, our 401(k) auditors directory can help you find the right firm.