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What Employers Need to Know About 401(k) Compliance & Fiduciary Duty

Written by The Payroll Company | Sep 2, 2025 2:00:00 PM

Offering a 401(k) plan is one of the most valuable benefits you can provide employees. It helps attract top talent, boosts retention, and demonstrates your commitment to their financial future. But with this powerful benefit comes significant responsibility.

As an employer sponsoring a 401(k) plan, you take on complex compliance obligations and fiduciary duties that carry real legal and financial consequences. Understanding these requirements isn't optional. It's essential for protecting your business, your employees, and yourself from costly mistakes that could result in penalties, lawsuits, and reputational damage.

This guide walks you through the critical compliance requirements and fiduciary responsibilities every employer needs to understand when managing a 401(k) plan.

Key Takeaways

  • 401(k) compliance involves multiple regulatory bodies including the DOL, IRS, and ERISA requirements
  • Employers have fiduciary duties to act solely in participants' best interests and manage investments prudently
  • Common compliance mistakes include late contribution deposits and failing to perform required testing
  • Regular audits, proper documentation, and working with qualified professionals help maintain compliance
  • Violations can result in significant penalties, lawsuits, and reputational harm

Understanding 401(k) Compliance

What Compliance Means

Compliance in the context of 401(k) plans means following all applicable laws, regulations, and your plan document requirements. It's a multi-layered responsibility that involves adhering to rules from several regulatory bodies:

The U.S. Department of Labor (DOL) oversees fiduciary responsibilities and participant protections under ERISA. The Internal Revenue Service (IRS) manages tax qualification requirements, contribution limits, and annual reporting. The Employee Retirement Income Security Act (ERISA) provides the foundational legal framework governing employer-sponsored retirement plans.

Key Compliance Requirements

  • Plan Documentation forms the foundation of compliance. Your written plan document serves as the rulebook for how your 401(k) operates. Every decision and action must align with what's stated in these documents.
  • Nondiscrimination Testing ensures your plan doesn't unfairly benefit highly compensated employees over rank-and-file workers. The ADP (Actual Deferral Percentage) and ACP (Actual Contribution Percentage) tests compare contribution rates between different employee groups annually.
  • Contribution Limits must be monitored carefully. The IRS sets annual limits for employee deferrals, employer matches, and total contributions. Exceeding these limits triggers correction requirements and potential penalties.
  • Timely Deposits require employee contributions to be deposited into the plan as soon as administratively feasible, but no later than the 15th business day of the following month for small plans.
  • Required Notices keep participants informed about their benefits. These include Summary Plan Descriptions, annual fee disclosures, and safe harbor notices when applicable.
  • Form 5500 Filing provides annual reporting to the DOL and IRS about your plan's financial condition, investments, and operations.

Employer Fiduciary Duties

What It Means to Be a Fiduciary

Under ERISA, a fiduciary is anyone who exercises discretionary authority over plan management, administration, or assets. This typically includes plan sponsors, administrators, and investment committee members.

Being a fiduciary means you're held to the highest standard of care when making decisions affecting plan participants. You're legally obligated to put participants' interests ahead of your own and act with the care of a prudent expert.

Core Responsibilities

  • Acting Solely in Participants' Interests means avoiding conflicts of interest and making decisions based solely on what benefits plan participants and beneficiaries. Personal or company financial interests cannot influence plan decisions.
  • Prudent Investment Management requires selecting and monitoring investment options with the same care a knowledgeable investor would use. This includes regular review of investment performance, fees, and appropriateness for your participant population.
  • Fee Reasonableness demands ongoing evaluation of all plan expenses. You must ensure fees paid for services are reasonable compared to the value provided and similar services in the marketplace.
  • Following Plan Documents means consistently adhering to the rules and procedures outlined in your plan documents. Deviations require formal plan amendments.
  • Diversification of Investments helps minimize risk by offering participants a range of investment options across different asset classes and risk levels.

Common Mistakes That Lead to Compliance Issues

Many employers unknowingly create compliance problems through seemingly minor oversights. Late deposits of employee contributions rank among the most frequent violations. Even delays of a few days can trigger DOL investigations and require corrective payments.

Skipping annual nondiscrimination testing is another costly mistake. These tests must be completed every year, and failure to do so can result in plan disqualification and significant tax consequences for all participants.

Fee oversight often gets overlooked until it becomes a problem. Plans that haven't reviewed fees in several years may be paying excessive amounts, exposing fiduciaries to breach of duty claims.

Outdated plan documents create compliance gaps when actual practices don't match written procedures. Regular document updates ensure your plan stays aligned with current operations and regulations.

Poor participant communication leaves employees uninformed about their benefits and can result in missed notice requirements that carry Department of Labor penalties.

How Employers Can Stay Compliant

Regular Plan Audits provide essential oversight. Whether conducted internally or by third-party professionals, these reviews identify potential issues before they become costly problems.

Working with a Trusted Third-Party Administrator (TPA) brings specialized expertise to complex compliance requirements. A qualified TPA handles testing, reporting, and notices while keeping you informed of your ongoing responsibilities.

Providing Ongoing Fiduciary Training ensures decision-makers understand their obligations and stay current with changing regulations. Well-trained fiduciaries make better decisions and reduce liability exposure.

Documenting All Decisions creates the paper trail necessary to demonstrate prudent processes. Meeting minutes, investment reviews, and fee analyses provide crucial protection if decisions are later questioned.

Using Payroll Integration, such as with an all-in-one software like isolved, reduces the risk of contribution errors and timing issues. Automated systems help ensure employee deferrals are calculated correctly and deposited promptly.

Consequences of Noncompliance

The stakes for 401(k) compliance failures are substantial. DOL and IRS penalties can range from hundreds to millions of dollars depending on the violation's severity and duration. Correction costs often exceed the original penalties, especially for issues that affect multiple plan years.

Employee lawsuits represent another significant risk. Participants can sue for breaches of fiduciary duty, excessive fees, or plan mismanagement. These cases often result in substantial settlements and legal fees.

Reputational damage affects your ability to attract and retain quality employees. News of retirement plan problems spreads quickly and can undermine employee trust in company leadership.

Protecting Your Business and Your Employees

401(k) compliance and fiduciary duty represent ongoing responsibilities that require consistent attention and expertise. Success depends on understanding the requirements, implementing proper procedures, and working with qualified professionals who can guide you through the complexities.

The integration of accurate payroll and benefits administration plays a crucial role in maintaining compliance. When your systems work together seamlessly, you reduce errors and ensure timely, accurate processing of contributions and reporting.

Don't navigate these challenges alone. The Payroll Company powered by isolved specializes in integrated payroll and retirement plan compliance solutions that help employers meet their obligations while providing valuable benefits to employees. Contact us today to learn how we can support your 401(k) compliance needs and protect your business from costly mistakes.