Preparing for a 401(k) Plan Audit: A Month-by-Month Sponsor Checklist
A smooth 401(k) plan audit is built month by month: reconcile data, preserve evidence, resolve exceptions early, and give the auditor a consistent story across payroll, trust, plan documents, and Form 5500.
A smooth 401(k) plan audit is built month by month: reconcile data, preserve evidence, resolve exceptions early, and give the auditor a consistent story across payroll, trust, plan documents, and Form 5500.
For a plan sponsor, the practical question is rarely just what the rule is. It is what to do next, what to preserve, and who should review the decision before a routine compliance matter becomes harder to correct.
At a glance
- Start with facts: identify the event, plan year, people, and records involved.
- Use the right lens: separate reporting, tax, fiduciary, audit, and insurance questions.
- Keep evidence: retain calculations, approvals, communications, and follow-up testing.
Define the decision
An annual audit can help protect plan assets and financial integrity while identifying control weaknesses or operating errors.[1] Preparation should therefore be a governance routine, not a document scramble after the plan year ends. The Form 5500 series is an annual reporting system shared by DOL, IRS, and PBGC, making reconciliation across records especially important.[2]
Begin with the governing plan document, the applicable year, and the actual operational record. Avoid filling gaps with assumptions. A short chronology—what occurred, who knew, what money or data moved, and what has already been done—gives the committee and advisers a shared starting point.
Compare the choices
Compare records by purpose. Payroll supports elective deferrals and employer contributions; the trust or custodian supports investments and cash movement; the census supports eligibility and account testing; plan documents support the operational rules; and the draft Form 5500 brings those strands together. A discrepancy is a question to investigate, not something to hide with a late adjustment.
| Question | Useful evidence | Next step |
|---|---|---|
| What happened? | Plan document, records, dates, and approvals | Write a neutral fact summary |
| Who is affected? | Census, account, payroll, and vendor data | Measure impact before choosing a remedy |
| Which rule applies? | Current agency guidance and professional advice | Confirm the correct compliance path |
Good decision-making is not about forcing every issue into a familiar label. It is about preserving options while the sponsor validates the facts, obligations, and available relief.
Questions to settle before action
Ask whether the plan document gives a clear answer, whether the records tell the same story across systems, and whether the issue affects a participant, the plan as a whole, or a filing obligation. Identify deadlines without guessing at them. If information is incomplete, record the open question and the person responsible for resolving it. This approach is more useful than treating uncertainty as evidence that no action is required.
Also separate a correction decision from a communication decision. A sponsor may need to coordinate with an auditor, recordkeeper, custodian, counsel, or participants, but the audience and timing should follow the facts and applicable requirements. Clear ownership, a documented decision, and a dated evidence file help prevent a small ambiguity from becoming a recurring operational weakness.
Implement with a record
At the start of the plan year, set owners and due dates. Midyear, test payroll feeds, contribution remittances, participant changes, and vendor reports. After year-end, freeze a clean census extract, reconcile trust activity, gather amendments and committee minutes, prepare requested schedules, and meet with the auditor before final Form 5500 work begins. Ask how the auditor will address contributions, benefit payments, eligibility, participant accounts, and prohibited transactions.[1]
Use a single owner for the workplan, but involve the people who control the underlying evidence. Payroll, the recordkeeper, trustee or custodian, counsel, accountant, and committee may each hold a necessary piece. Document requests and responses contemporaneously; reconstructed explanations are less reliable than records created during the work.
Practical workplan
| Stage | Sponsor action | Completion evidence |
|---|---|---|
| Define | Confirm the facts and applicable period | Chronology and source documents |
| Compare | Evaluate the relevant correction, filing, audit, or coverage path | Written analysis and adviser input |
| Implement | Complete approved actions and required communications | Calculations, approvals, receipts, and notices |
| Review | Test the new control and report to the committee | Follow-up log and meeting record |
Review and prevent recurrence
Review every exception through closure. Record the issue, affected period, root cause, corrective action, approver, and evidence of completion. The same tracker can drive the next year’s preventive controls and give the committee a practical view of audit readiness.
Use the review to improve the calendar, not merely close a file. A concise committee report should distinguish confirmed facts from open questions, identify any participant-facing communication, and name the next review date. This creates continuity when staff, vendors, or committee members change.
Make the control usable
A preventive control should be specific enough that a new employee can operate it. Name the input, the reviewer, the cadence, the exception threshold, and the location where evidence is saved. For example, an owner may reconcile a payroll report to a trust report each month, route exceptions to a committee designee, and retain the signed reconciliation in a shared compliance folder. The point is not bureaucracy; it is making a critical handoff observable.
Schedule a short post-completion check rather than waiting for the next annual cycle. Confirm that payments, filings, notices, or record changes were accepted where applicable; compare the final result to the original fact summary; and make sure all required records are retained. If facts change after the initial analysis, update the chronology and ask advisers whether the change affects the selected path. Closing the loop is part of the work.
Committee minutes should capture the decision at an appropriate level: what was reviewed, what was approved, which matters were delegated, and when progress returns to the committee. They need not repeat sensitive details, but they should be sufficient to show thoughtful oversight. A reliable record protects participants and helps the sponsor respond consistently to future questions.
Takeaway
Start with a complete fact record, select the compliance path that matches the issue, and retain proof of both correction and prevention. That disciplined sequence helps sponsors make defensible decisions without overstating what any one program, audit, bond, or filing can accomplish.
Editorial disclaimer: This article is general educational information, not tax, legal, actuarial, investment, insurance, or compliance advice. Retirement-plan obligations depend on the plan document, facts, and current law. Consult qualified advisers before acting.
References
- [1] Selecting an Auditor for Your Employee Benefit Plan — https://www.dol.gov/sites/dolgov/files/EBSA/about-ebsa/our-activities/resource-center/publications/employee-benefit-plan-auditor-selection.pdf
- [2] Changes for the 2023 Form 5500 and Form 5500-SF Annual Return/Reports — https://www.dol.gov/agencies/ebsa/about-ebsa/our-activities/resource-center/fact-sheets/changes-for-the-2023-form-5500-and-form-5500-sf-annual-return-reports