Preparing for a 401(k) audit isn’t just about gathering paperwork—it’s about providing the exact documents your auditor expects, in a format they can actually use.

If items are missing, incomplete, or inconsistent with how your plan operates, audits get delayed—and risk increases.

This guide breaks down what auditors actually request, how those materials are used, and how to organize them so your audit runs smoothly.

New to 401(k) audits? Start with our complete guide to requirements, timelines, and what to expect → Grab the Guide

What auditors look for (and why it matters)

Auditors aren’t just collecting documents—they’re testing whether your plan is:

• Operating according to the plan document
• Complying with IRS and DOL requirements
• Accurately reporting financial activity

Every document you provide supports one of those objectives. Missing or inconsistent information is what typically slows audits down.

Plan Documents (Core Foundation)

These documents should be available for all plan years and should be the signed, executed versions.

• Basic Plan Document
• Adoption Agreement
• Summary Plan Description (SPD)
• Summary of Material Modifications (SMMs; if applicable)
• IRS Opinion/Determination Letter
• Investment and Fund Agreements
• Annuity, Common Collective Trust and/or Stable Value Contracts

Service Provider Agreements 

Auditors use these to understand roles, responsibilities and controls.

• Record keeping Agreement
• Custodial Agreement
• Investment Advisory Agreement
• Banking Agreement (if applicable)
• Insurance Policy (if applicable)
• Service Agreements over functions such as electronic distribution of documents
• SOC Reports from various providers (Payroll Company, Record-keeper and Custodian) including IT support for all areas.

Compliance and Regulatory Documentation

This is where auditors validate plan compliance.

• Current and prior year discrimination testing
• Documentation related to correction of Plan testing failures
• Plan census data (current and prior year)
• Form 5500 filings (current and prior year)
• Current Year Plan Disclosures and documentation of how and when they were distributed
• Copies of 1099-R’s issued for the Plan participants or a report showing this information
• Fidelity bond copy
• Related Party and Party-in-interest Listings and description of transactions involving these parties.
  

Internal Controls and Processes

These are often overlooked, and a common source of issues. Provide documented processes for:

• Employee enrollment
• Contribution processing
• Distributions and Loans
• Plan level access (administrative access)
• Higher level review of the Plan (monitoring of Plan activity)
• Payroll processes and setup of new employees
• Payroll processes and setup of a new loan for the participant
• Payroll processed and termination procedures

Payroll and Testing Support

Auditors will sample this heavily

• Year-end payroll reports
• Specific pay period reports for sample items
• W-2 Copies for Sample items

Financial and Investment Records

• Trust Report
• Activity Reports such as Contribution, Distribution, Fee and Loan reporting
• Schedule of Assets
• Custodial Certification
• Custodial Statements (if applicable)
• Bank Statements
• Insurance Policy year-end information
• Participant Statement Copies or a report providing information on participant accounts showing the investment information and sub-account information (pre-tax account, rollover account, employer accounts, etc. for each participant).

Testing Information

• I-9 Forms
• Enrollment and Deferral Change Forms
• Decline of Enrollment Forms (if applicable)
• Distribution requests or a report showing this information
• Loan requests or a report showing this information
• Promissory note copies and amortization schedules
• Check copies or a report showing the distribution or loan issuance
• Reports showing investment selections made by a participant
• Rollover supporting documentation

Closing and Audit Support Items

• Management Representation Letter
• Attorney Representation Letter (if applicable)
• Review of Financial Statements and Disclosures
• Discussion with the auditor regarding any issues noted during the year

Where most plans run into issues

Even when documents exist, audits slow down when:

• Prior-year records aren’t retained (especially for first-time audits)
• Payroll and plan data don’t reconcile
• Internal processes aren’t documented
• Corrections lack supporting documentation

This is why a clear document retention policy is critical—auditors are required to verify beginning balances, which often means reviewing multiple prior years.

Reduce Audit Time and Limit Disruption with Organized Documents

While this is not meant to be a complete listing of all the information that will be needed for a 401(k) Plan audit, it can be used as a checklist to prepare for an upcoming audit.

When your audit approaches, having the right documents organized and review-ready can reduce audit time, limit disruption, and prevent costly delays.

At Anders, we specialize in 401(k) audits and can guide you through exactly what’s needed—before your audit begins. To get started, request a free 401(k) audit consultation below.