Solo 401k Reporting Requirements for 2025

A Solo 401k can be a powerful way for self-employed individuals and small-business owners to save for retirement. But along with the benefits come certain responsibilities, including annual reporting.

If you’re starting a new plan or checking whether your existing one is still compliant, it’s important to understand what’s required. Failing to file Form 5500-EZ on time or reporting assets incorrectly could lead to penalties or even trigger an IRS audit.

This guide covers the key Solo 401k reporting requirements. You’ll learn who needs to file, which IRS forms are required, and the deadlines to track. We’ll also explain how to file online, how to request an extension if needed, and how to keep your records in good order.

📌 Also Read: 15 Solo 401k Facts to Know in 2025 (Contributions, Rules, and Strategies)

Solo 401k Reporting: What to Know

Solo 401k plans don’t fall under the same level of oversight as large employer-sponsored plans. However, the IRS still requires certain filings to make sure your plan stays compliant.

These filings serve a few key purposes: they document your plan’s financial status, show that it’s being managed properly, and help preserve the tax benefits tied to your retirement savings.

There are two main areas every Solo 401k owner should understand: who must file and which forms may be required.

Who Needs to File and When

If you have a Solo 401k and your total plan assets are more than $250,000 at the end of the plan year (usually December 31), the IRS requires you to file Form 5500-EZ each year.

This rule also applies if you’re closing the plan, regardless of the account balance.

The deadline to file is July 31 of the following year. If you need extra time, you can request an extension by submitting Form 5558 before the original due date.

Filing Requirements at a Glance:

✅ You’re self-employed with no full-time employees (except your spouse)

✅ Your Solo 401k assets are over $250,000 as of December 31

✅ Or you’re terminating the plan, no matter the balance

IRS Forms You Might Need

Here are the main IRS forms tied to Solo 401k reporting, depending on your plan’s activity:

✅ Form 5500-EZ – Reports your plan’s annual financials. Required if assets exceed $250,000 or if you’re closing the plan. 

✅ Form 5558 – Used to request a 2.5-month extension to file Form 5500-EZ.

✅ Form 1099-R – Required if you took distributions or rollovers during the tax year. Each distribution must be reported in the tax year it happened.

How to File & Meet the Deadline

Filing your Solo 401k reports accurately and on time is a key part of staying compliant with IRS rules. 

Here’s how to file, how to request more time, and what happens if you miss the deadline.

E-Filing Basics & Signature Rules

If your Solo 401k plan exceeds $250,000 in assets or is terminated during the year, you’ll likely need to file Form 5500-EZ.

While paper filing is still allowed, the IRS strongly encourages using its EFAST2 system to file electronically. Starting January 1, 2025, you’ll have the option to file Form 5500-EZ either by mail or through EFAST2. Just note that the regular IRS e-File system (used for income taxes) cannot be used for this form.

Key points to remember:

✅ Create an account on the Department of Labor’s EFAST2 website
✅ Electronic submissions require a PIN and must be signed by the plan administrator
✅ Do not submit Form 5500-EZ through IRS e-File

📝 Note: If you prefer to mail the form, use the paper version of Form 5500-EZ and carefully follow the IRS mailing instructions.

How to Get a Filing Extension

Need more time to file? You can request an automatic 2.5-month extension by submitting Form 5558 before the original July 31 deadline. This typically extends your filing date to October 15 for calendar-year plans.

✅ File Form 5558 on or before July 31 (or through EFAST2 starting January 1, 2025)
✅ No IRS approval is needed—just filing the form grants the extension
✅ Form 5558 must be mailed—there’s no e-file option available for it

📝 Tip: Be sure to keep a copy of your Form 5558 submission as proof, in case the IRS requests it later.

What Happens if You File Late

Late filings can lead to serious penalties — $250 per day, up to $150,000 per return, under IRC Section 6652(e). However, the IRS does offer penalty relief for some late filers.

Under Revenue Procedure 2015-32, one-participant plans may qualify for a reduced fee of $500 per return, up to a $1,500 cap per plan, if they meet the requirements under the IRS Late-Filer Penalty Relief Program.

If you started your plan late under the SECURE Act, you may still be able to adopt the plan retroactively for the prior tax year (up to your tax filing deadline, including extensions). But you still need to file if your plan assets go over the threshold or if the plan is terminated.

📌 Remember:

Staying Compliant With Your Solo 401k

Staying compliant with your Solo 401k involves more than just filing forms. You also need to keep proper records and understand what’s required during important events, like when you close the plan.

This section covers what documents to keep, how long to keep them, and common mistakes to avoid. These small steps can help you avoid issues and stay on the IRS’s good side.

How Long to Keep Records

The IRS expects Solo 401k sponsors to keep all documents that support the plan’s compliance and yearly filings. These include:

✅ Signed copies of your original plan documents and amendments
✅ Records of contributions and distributions
✅ Filed copies of Forms 5500-EZ or 5500-SF
✅ Account statements showing plan assets and activity
✅ Loan repayment records, if applicable

📝 Note: Section 107 of ERISA also requires records to be kept for six years after each Form 5500-EZ is filed. Many advisors suggest keeping them until all benefits are paid out and the audit period has ended. 

Filing in Your Final Plan Year

If you’re closing your Solo 401k, you must file a final Form 5500-EZ, even if plan assets are under $250,000.

Be sure to check the box on the form to indicate it’s your final return. The $250,000 threshold still applies, but once you’ve hit that level in a previous year, a final filing is always required.

📌 Remember:

Common Mistakes to Avoid

Avoid these frequent errors, which could trigger penalties or draw IRS attention:

❌ Not filing Form 5500-EZ after your assets exceed $250,000
❌ Filing late or using an outdated version of the form
❌ Forgetting to check the “final return” box when closing the plan
❌ Losing track of key records or failing to maintain documentation

Remember, taking a proactive approach can help you avoid these issues and keep your Solo 401k fully compliant year after year.

Wrapping Up Your Solo 401k Reporting Checklist

Solo 401k reporting can seem technical at first, but once you understand the basic requirements, it becomes easier to manage year after year. Knowing which forms to file, when they’re due, and how to stay organized can help you avoid unnecessary penalties and keep your retirement plan in good standing.

Stay consistent with recordkeeping and review IRS updates each year. And if your situation becomes more complex—such as closing the plan or taking distributions—it may be worth consulting a tax professional to make sure everything is reported correctly.

📌 For more Solo 401k guidance, explore our related articles on contributions, withdrawals, and plan design options.

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