Written By: Neil Tremblay
When plan sponsors think about fiduciary risk, they often focus on investments, fees, or compliance testing. But one of the most common and most costly sources of operational failure in a 401(k) plan is far less visible: payroll codes.
Specifically, whether each pay code is properly classified as eligible for employee deferrals, eligible for employer match or non-elective contributions, or excluded from one or more. This may sound administrative, but in practice, it is one of the most important controls in your plan.
Why Payroll Code Accuracy Matters
Your plan document defines what compensation is eligible for deferrals, matching contributions, nonelective contributions, and testing compensation. Payroll systems, however, operate on pay codes (e.g. salary, bonus, overtime, commissions, allowances, fringe benefits, etc.) If these two frameworks are not aligned, the plan will not operate according to its written terms. And under ERISA, that is a fiduciary failure.
Where Things Go Wrong
In our experience, payroll code issues typically arise from:
- New pay codes introduced without review. HR or payroll adds a new code (e.g., “Retention Bonus” or “Auto Allowance”) without evaluating whether it is eligible compensation under the plan document, or whether it should be included for match or non-elective contributions.
- Legacy coding decisions that were never validated. Many plans inherit payroll setups that were implemented years ago, never reconciled to the plan document, or were incorrect from the start.
- Mismatches between deferral and match and/or non-elective contribution eligibility. A code may be included for deferrals but excluded for match or non-elective contribution (or vice versa), inconsistent with plan provisions.
- Fringe benefits and special pay. Items such as auto allowances, tax gross-ups, certain bonuses, etc. often fall under nuanced rules (e.g., Treasury Reg. §1.414(s)-1) and are frequently misclassified.
The Real Cost of Getting It Wrong
These are not theoretical issues. When payroll codes are misaligned, the consequences can be significant:
- Missed deferrals. If compensation should have been eligible for deferral, but wasn’t, the plan must fund a QNEC (Qualified Nonelective Contribution) plus lost earnings.
- Missed match contributions. If match-eligible pay was excluded, the employer must make corrective match contributions, often with lost earnings.
- Ineligible Deferrals and Match. If compensation was incorrectly included as eligible, contributions must be refunded or reallocated, and earnings must be adjusted. As a result, participant communications become complex and sensitive.
- Compliance Testing Distortions. Incorrect compensation definitions can impact ADP/ACP testing, 415 limits, and Top-heavy calculations.
- Audit and IRS Exposure. From an audit perspective, this is a major red flag. Auditors routinely test payroll mapping, and errors suggest weak internal controls. Issues may need to be disclosed in the audit. From an IRS standpoint, errors can require correction under EPCRS, and repeated failures suggest systemic noncompliance.
Unlike a missed deposit or one-time mistake, payroll code errors repeat every payroll cycle, affect every participant paid under that code, and can go undetected for years. We have seen cases where errors persisted for 3–5+ years and the correction costs reached six figures or more.
What a Strong Governance Process Looks Like
A well-run plan does not leave this to chance. Plan sponsors should implement a formal payroll code governance process, including:
Initial Payroll Code Audit
- Inventory all payroll codes
- Map each code to plan document definitions:
- Deferral eligibility
- Match eligibility
- Testing compensation
Annual (or More Frequent) Reviews
- Reconcile payroll codes to the plan document
- Confirm no changes were made without review
Change Management Controls
- Before adding or modifying a pay code:
- Require review against plan provisions
- Document the determination
Documentation and Sign-Off
- Maintain a payroll code mapping file
- Document decisions
- Initiate a periodic sign-off by HR/payroll and plan fiduciaries
Coordination with Recordkeeper and Advisor
- Ensure payroll system coding aligns with recordkeeper feeds
- Ensure contribution calculations reflect intended definitions
The Role of a Retirement Plan Advisor
This is where a strong advisor adds real value. A prudent retirement plan advisor should:
- Lead the payroll code audit process
- Translate plan document provisions into operational rules
- Identify inconsistencies and risk areas
- Coordinate with payroll and recordkeeping teams
- Establish ongoing monitoring procedures
- Document the process for fiduciary protection
In our view, this is not optional, it is a core part of fiduciary governance.
Payroll coding may not be visible to participants, but it sits at the heart of your plan’s operational integrity. If your payroll codes are not aligned with your plan document, your plan is not operating correctly, and errors are accumulating in the background. The cost of fixing them is growing every day, and the solution is straightforward: audit, document, and monitor.
Have additional questions? Connect with our team today.
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