If your Solo 401(k) plan assets crossed $250,000 last year, you are required to file IRS Form 5500-EZ. It is not a complicated form, but the details matter. A missed filing or an error can trigger penalties of $250 per day, up to $150,000 per return.

This guide walks through everything you need to know: the 2026 contribution limits, whether you are required to file, how to complete the form line by line, and what happens if you miss the deadline.

2026 Solo 401(k) Contribution Limits

Before looking at the form itself, it helps to know where the 2026 limits stand. Higher contribution limits mean your plan balance can grow faster than in prior years, which means you may cross the $250,000 filing threshold sooner than expected.

One important SECURE 2.0 reminder: under SECURE 2.0, employees aged 50 or older with prior-year FICA wages exceeding $150,000 must make catch-up contributions as Roth after-tax contributions starting in 2026.

Do You Need to File IRS Form 5500-EZ?

The filing requirement hinges on your total plan asset value on December 31 of the plan year.

Under $250,000: If the combined value of your Solo 401(k) assets, including any other one-participant plans your business sponsors, is $250,000 or less at year end, you are exempt from filing. No action required.

Over $250,000: Once your combined plan assets exceed $250,000, you must file Form 5500-EZ for that year and every year going forward, even if your balance dips back below the threshold due to market fluctuations.

Final year rule: Regardless of your account balance, you must file a final Form 5500-EZ when you fully terminate the plan and distribute all assets. This tells the IRS the plan is officially closed.

Electronic vs. Paper Filing

The IRS requires any filer who submits 10 or more returns of any type during the calendar year, including W-2s, 1099s, income tax returns, and employment tax returns, to file Form 5500-EZ electronically through the Department of Labor’s EFAST2 system.

If you issue 1099s to independent contractors alongside your personal and business tax filings, there is a good chance you will hit that threshold and be required to file electronically.

Filing electronically: You must use the EFAST2 web-based filing system or IRS-approved third-party software. A standard PDF upload is not accepted.

Filing on paper: If you fall below the 10-return threshold, you can mail a paper filing. Use the official fillable form from the IRS website, print it, and sign in blue or black ink. Hand-written edits or non-standard pens can trigger processing errors and automated penalty notices.

How to Complete IRS Form 5500-EZ: Line by Line

IRS Form 5500-EZ is a two-page document. Have your year-end financial statements, business EIN, and plan documents on hand before you start.

Part I: Annual Return Identification

Plan year dates: Enter the start and end dates of your plan year. For a calendar-year plan, that is 01/01/2025 to 12/31/2025 for the 2025 filing year.

Box A: Check box (1) if this is the first time this plan has ever filed a 5500-EZ. Check box (3) if you fully terminated the plan and distributed all assets during the year. If neither applies, leave both blank.

Box B: If you filed for an extension via Form 5558 or qualify for an automatic business tax extension, check the appropriate box here.

Part II: Basic Plan Information

Lines 1a and 1b: Enter the formal name of your plan as it appears on your adoption agreement and your three-digit plan number. For most first-time filers, that number is 001.

Line 1c: Enter the date the plan originally went into effect.

Lines 2a and 2b: Enter your business name, mailing address, and Employer Identification Number. Do not use your personal Social Security number here. If your Solo 401(k) does not have its own EIN, request one from the IRS before filing.

Line 2d: Enter the six-digit NAICS code that matches your primary business activity. This is the same code used on your Schedule C or business tax return.

Lines 3a through 3c: If you administer the plan yourself, write “SAME” on Line 3a and leave the rest of this section blank.

Lines 5a through 5c: If you are the only participant, enter “1” across these fields. If your spouse also participates and holds a balance, enter “2.”

Part III: Financial Information

Line 6a: Enter the total value of all plan assets at the beginning of the plan year in Column 1 and at the end of the plan year in Column 2. This includes cash, equities, real estate valuations, cryptocurrency, and any other holdings.

Line 6b: Enter any debts or outstanding claims against the plan. For most Solo 401(k) filers who are not using leverage or non-recourse loans, this is zero.

Line 7: Break out contributions for the year. Enter employer profit-sharing contributions in 7a, employee elective deferrals in 7b, and any rollovers from other retirement accounts in 7c.

Part IV and V: Plan Characteristics and Compliance

Line 8: Enter the alphanumeric codes that describe your plan’s features. Common codes for a Solo 401(k) include:

• 2E: Profit-sharing plan
• 2J: Contains a cash or deferred arrangement, such as a pre-tax elective deferral option
• 3D: Plan permits designated Roth contributions

Line 9: Check Yes or No to confirm whether the plan experienced any non-exempt prohibited transactions. If you have an active participant loan, check Yes and enter the outstanding loan balance as of December 31.

Lines 10 and 11: These apply to defined benefit plans subject to minimum funding rules. For a standard Solo 401(k), check No.

Line 12 (New IRS Compliance Line): This line asks whether your plan is operating under a pre-approved plan document. If you are using a prototype or volume submitter plan from an approved provider, check Yes and enter the exact IRS Opinion Letter date issued to your plan provider. This date confirms that the plan documents reflect current legislation, including SECURE Act updates. Contact your plan provider if you are not sure of this date.

Deadlines, Extensions, and Penalties

The filing deadline for Form 5500-EZ is July 31 for calendar-year plans, which is the last day of the seventh month following the end of the plan year.

Need more time? File IRS Form 5558 on or before July 31 to request an automatic 2.5-month extension, moving your deadline to October 15. If your business tax return has been extended and your plan year matches your business tax year, that extension may automatically apply to your 5500-EZ filing as well.

Late filing penalties: The penalty for missing the deadline is $250 per day, up to a maximum of $150,000 per unfiled return. If you have a missed filing from a prior year, the IRS Late Filer Penalty Relief Program allows you to submit the delinquent return and significantly reduce the penalties owed.

Filing as an IRA Financial Client

If your Solo 401(k) is administered through IRA Financial, our team can handle the Form 5500-EZ filing on your behalf. We manage the preparation, ensure your plan documents are current for Line 12 reporting, and maintain the compliance records needed to keep your plan in good standing.

If you have questions about your filing requirements or want to confirm whether your plan is set up correctly before the July 31 deadline, our team is available for a free consultation.