Offering a 401(k) plan is one of the most valuable investments a small business can make in its employees. But sponsoring a retirement plan also comes with compliance responsibilities that extend far beyond payroll deductions and annual filings.

One of the most important and frequently misunderstood requirements is nondiscrimination testing.

Many small business owners don't think about nondiscrimination testing until their third-party administrator (TPA) sends an email saying the plan has failed. By then, employers may be facing corrective distributions, additional employer contributions, or administrative headaches they didn't anticipate.

At Basic Capital, we believe compliance should be proactive, not reactive. Understanding how nondiscrimination testing works can help employers avoid costly surprises while building a retirement plan that benefits everyone.

This guide explains what 401(k) nondiscrimination testing is, who it applies to, how it works, and what employers can do to reduce compliance risk.

What Is 401(k) Nondiscrimination Testing?

Nondiscrimination testing is a series of annual IRS-required tests designed to ensure a company's retirement plan benefits employees fairly, not just owners, executives, or highly compensated employees (HCEs).

The goal is straightforward.

A 401(k) plan should provide meaningful retirement savings opportunities across the workforce rather than disproportionately benefiting higher-paid employees.

Most traditional 401(k) plans complete these tests each year as part of their compliance process.

Why Nondiscrimination Testing Matters

Passing nondiscrimination testing is about more than satisfying an annual compliance requirement.

It helps employers:

• Maintain the plan's tax-qualified status while meeting IRS requirements for retirement plans.

• Ensure retirement benefits remain equitable across different employee groups.

• Reduce the likelihood of corrective distributions or unexpected employer contributions.

• Demonstrate sound governance of retirement plans and fiduciary oversight.

For growing businesses, understanding these requirements early makes long-term plan administration much easier.

Which Plans Must Complete Nondiscrimination Testing?

Most traditional 401(k) plans are required to complete annual testing.

However, some Safe Harbor 401(k) plans are exempt from certain annual nondiscrimination tests because they satisfy IRS requirements through mandatory employer contributions and specific notice requirements.

This is one reason many growing businesses choose Safe Harbor plan designs as they scale.

The Three Primary Nondiscrimination Tests

Although retirement plan compliance involves multiple requirements, employers will most commonly encounter three tests.

Actual Deferral Percentage (ADP) Test

The ADP test compares salary deferral rates between:

• Highly compensated employees (HCEs)

• Non-highly compensated employees (NHCEs)

The objective is to ensure that higher-paid employees do not contribute significantly more than the rest of the workforce.

If participation among non-highly compensated employees is too low, highly compensated employees may have their contribution limits effectively reduced.

Actual Contribution Percentage (ACP) Test

The ACP test evaluates employer matching and after-tax employee contributions.

Like the ADP test, it compares participation between highly compensated and non-highly compensated employees to confirm employer contributions are being distributed fairly.

Companies offering generous matching programs should pay close attention to ACP testing because matching formulas directly affect test results.

Top-Heavy Test

The Top-Heavy Test evaluates whether more than 60% of total retirement plan assets belong to key employees.

If the plan becomes top-heavy, employers may need to make minimum employer contributions for eligible non-key employees.

This test is especially relevant for founder-led businesses and closely held companies where ownership groups participate heavily in the retirement plan.

Who Is Considered a Highly Compensated Employee?

For nondiscrimination testing purposes, an HCE generally includes employees who meet IRS compensation thresholds or ownership requirements.

Examples often include:

• Company owners

• Executives

• Senior leadership

• Employees whose compensation exceeds annual IRS limits

Because IRS thresholds are updated periodically, employers should work with their retirement plan administrator or advisor to determine current eligibility.

Common Reasons Plans Fail Nondiscrimination Testing

Many compliance failures stem from employee participation patterns rather than administrative errors.

Common causes include:

Low Participation Among Rank-and-File Employees

When fewer non-highly compensated employees participate, contribution rates between employee groups become less balanced.

Highly Compensated Employees Maximize Contributions

Owners and executives often contribute aggressively to retirement plans.

If participation among other employees remains low, the plan may struggle to satisfy ADP or ACP testing requirements.

Workforce Growth

Rapid hiring can change employee demographics and affect testing outcomes from year to year.

Companies experiencing significant growth should periodically review participation trends rather than waiting for annual testing results.

Inconsistent Employer Match Participation

Changes to matching formulas or uneven employee participation can influence ACP test results.

What Happens If Your Plan Fails?

A failed nondiscrimination test does not automatically jeopardize the retirement plan.

However, employers generally need to take corrective action.

Depending on the circumstances, corrections may include:

• Refunding excess contributions made by highly compensated employees.

• Making Qualified Nonelective Contributions (QNECs) to eligible employees.

• Adjusting employer matching contributions.

• Modifying future plan design to reduce recurring compliance issues.

The appropriate correction depends on the specific test that failed and the plan's overall structure.

How Small Businesses Can Improve Compliance Outcomes

The best compliance strategy focuses on preventing failures before annual testing occurs.

Encourage Broader Employee Participation

Higher participation among eligible employees often improves nondiscrimination testing results.

Employers can support participation through:

• Automatic enrollment

• Financial education

• Clear employee communications

• Simplified enrollment processes

Review Plan Design Regularly

Retirement plans should evolve as companies grow.

Periodic reviews of:

• Matching formulas

• Eligibility rules

• Automatic features

• Safe Harbor eligibility

can improve both employee participation and compliance outcomes.

Monitor Participation Throughout the Year

Waiting until year-end testing may limit available correction options.

Tracking participation trends throughout the year allows employers to identify potential issues earlier.

At Basic Capital, we believe proactive monitoring helps employers make informed plan decisions before compliance challenges become larger administrative projects.

The Value of Real-Time Compliance Monitoring

Traditional compliance processes often rely heavily on year-end testing.

Modern retirement platforms increasingly support ongoing visibility into plan health.

Rather than waiting for annual testing results, employers may benefit from monitoring:

• Employee participation rates

• Deferral trends

• Highly compensated employee contribution patterns

• Employer match utilization

• Potential testing risks throughout the year

Real-time compliance monitoring doesn't replace formal nondiscrimination testing, but it can provide earlier insight into trends that may affect year-end results.

For growing businesses, this proactive approach can reduce surprises and make retirement plan administration more predictable.

When Safe Harbor Plans May Be Worth Considering

Some employers choose a Safe Harbor 401(k) because it simplifies certain compliance requirements.

Safe Harbor plans generally:

• Eliminate ADP testing.

• Eliminate ACP testing.

• Encourage higher employee participation.

• Allow owners and highly compensated employees greater flexibility in contributions.

While Safe Harbor plans involve mandatory employer contributions, many businesses find the simplified compliance structure worthwhile.

The right approach depends on company size, workforce demographics, and long-term retirement goals.

Why Modern Retirement Platforms Support Better Compliance

Compliance should not depend on discovering problems after they occur.

Modern retirement platforms increasingly help employers by providing:

• Automated compliance workflows

• Payroll integrations

• Participation reporting

• Employer dashboards

• Ongoing plan monitoring

• Administrative support

At Basic Capital, we believe retirement technology should simplify compliance while giving employers greater visibility into their retirement plan's health.

Companies evaluating retirement plan solutions can also explore our For Employers resources.

Building a Stronger Compliance Strategy

Nondiscrimination testing is one of the most important compliance requirements for employer-sponsored retirement plans, but it doesn't have to be overwhelming.

By understanding how the tests work, encouraging employee participation, reviewing plan design regularly, and monitoring compliance year-round, employers can reduce administrative surprises and build a stronger retirement program.

At Basic Capital, we believe the best compliance strategy combines thoughtful plan design with modern technology that provides visibility into issues before they become problems.

Ready to simplify retirement plan administration and compliance? Get started with Basic Capital to learn how our platform helps employers streamline compliance, improve participation, and build retirement plans designed for long-term success.