Managing a 401(k) plan involves more than annual enrollment and payroll deductions. Employers are also responsible for meeting a long list of compliance deadlines throughout the year.

Missing key filing dates or participant notice requirements can create unnecessary penalties, compliance risks, and administrative challenges for HR and finance teams.

At Basic Capital, we believe retirement plan administration should feel more organized, transparent, and manageable. A clear compliance calendar can help employers stay ahead of deadlines while reducing operational stress throughout the year.

Below is a practical 2026 401(k) compliance checklist covering some of the most important deadlines plan sponsors should keep on their radar.

January 2026

Review Annual Compliance Testing Preparation

At the start of the year, HR and finance teams should begin preparing for annual nondiscrimination testing and prior-year compliance reviews.

Key areas to review include:

• Employee contribution rates and participation trends

• Highly compensated employee contribution activity

• Employer match calculations

• Payroll integration accuracy

• Eligibility tracking and employee classifications

For employers repeatedly struggling with ADP or ACP testing, this may also be an appropriate time to evaluate whether a safe harbor 401(k) structure could simplify compliance obligations.

Distribute Required Safe Harbor Notices

Plans using safe harbor provisions generally need to distribute annual notices to eligible participants before the beginning of the plan year.

These notices typically explain:

• Employer contribution formulas

• Employee rights and obligations

• Plan features and eligibility rules

Employers should confirm notices are delivered accurately and documented properly.

March 2026

Complete Prior-Year Nondiscrimination Testing

Most calendar-year plans should finalize:

• ADP testing

• ACP testing

• Top-heavy testing

If failures occur, corrective actions may need to happen quickly to avoid additional compliance complications.

Companies experiencing repeated testing failures may benefit from reviewing our:
Safe Harbor 401(k) Guide for Plan Sponsors

Review Employee Deferral Limits and Payroll Systems

Contribution limits and catch-up contribution rules should be reviewed annually to ensure payroll systems remain aligned with current IRS limits.

Errors tied to contribution caps or payroll integrations can create avoidable correction work later in the year.

April 2026

File Corrective Distributions if Needed

If nondiscrimination testing failures require corrective refunds to highly compensated employees, employers should ensure distributions are processed within required IRS timeframes.

Delayed corrections may create:

• Additional excise taxes

• Reporting complications

• Increased administrative burden

This is also a good time to review overall participation trends and employee engagement levels.

July 2026

File Form 5500 Extensions if Necessary

For calendar-year plans, Form 5500 filings are generally due by July 31 unless an extension is filed.

Form 5500 reporting includes:

• Plan financial information

• Participant counts

• Service provider details

• Compliance disclosures

Because this filing becomes publicly accessible, accuracy and completeness matter.

Many employers also use this period to review plan fees, investment structures, and advisor relationships.

August–September 2026

Review Plan Participation and Retirement Readiness

Midyear is a valuable time to assess:

• Participation rates

• Deferral trends

• Employee engagement

• Employer contribution forecasting

Modern retirement platforms can provide better visibility into participation behavior and compliance trends throughout the year rather than only during annual reviews.

At Basic Capital, we believe stronger real-time reporting and participant visibility help employers proactively manage retirement plans instead of reacting to issues after year-end testing.

Evaluate Open Enrollment Communication Strategies

As open enrollment planning begins, employers should review:

• Enrollment education materials

• Contribution guidance

• Financial wellness communication

• Retirement participation campaigns

Clear communication often plays a major role in improving long-term participation and reducing future testing challenges.

October 2026

Review Safe Harbor Contribution Structures for Next Year

Employers considering changes to:

• Matching formulas

• Safe harbor provisions

• Employer contribution strategies

• Plan design structures

should begin planning well before year-end.

Retirement plan design decisions often affect:

• Participation behavior

• Compliance outcomes

• Employer contribution forecasting

• Recruiting and retention strategies

Companies evaluating modernization opportunities can also explore our:
For Employers resources to learn how modern retirement infrastructure can simplify administration and improve participant experiences.

December 2026

Finalize Year-End Contribution Reviews

Before year-end closes, employers should review:

• Employee contribution totals

• Catch-up contribution eligibility

• Employer match calculations

• Payroll reconciliation

• Participant eligibility updates

This review helps reduce correction work during the next compliance cycle.

Prepare for the 2027 Plan Year

Year-end is also an ideal time to evaluate:

• Plan administration workflows

• Payroll integrations

• Advisor relationships

• Participant engagement trends

• Overall retirement plan performance

For many companies, year-end planning also creates an opportunity to evaluate whether their current retirement platform still supports the needs of a growing workforce.

Why a Strong Compliance Process Matters

401(k) compliance is not just about avoiding penalties. Strong retirement plan administration can also improve:

• Employee trust

• Retirement readiness

• Participation consistency

• Administrative efficiency

• Long-term plan scalability

At Basic Capital, we believe modern retirement infrastructure should help employers stay ahead of compliance requirements while creating better retirement experiences for employees.

That includes:

• Streamlined administration

• Transparent plan management

• Modern payroll integrations

• Better participant visibility

• Real-time reporting tools

As retirement plans become more complex, employers with stronger operational systems and clearer compliance visibility may be better positioned to support both their workforce and their long-term retirement strategy.

Ready to simplify retirement plan administration in 2026? Get started with Basic Capital to learn how our platform helps employers streamline compliance management, improve retirement outcomes, and modernize the employee retirement experience.