Handbook / Retirement accounts

Form 5500-EZ for solo 401(k) plans: who files and when (2026 plan year)

Tax-year note: Tax information on this page applies to the 2026 tax year (returns filed in 2027), from IRS pages checked in November 2026. Figures and dates are labelled with their tax year where they appear. Check current IRS pages before you rely on them.

A solo 401(k) is one of the most generous retirement plans for self-employed people. It comes with one recurring piece of paperwork that is easy to forget: Form 5500-EZ, the annual return for one-participant plans. Most small plans do not need to file at first, but once assets grow, or when the plan ends, filing becomes mandatory and late penalties can be significant. This guide covers the rules for the 2026 plan year.

What Form 5500-EZ is

Form 5500-EZ is the annual return of a one-participant retirement plan. The IRS describes a one-participant plan as a retirement plan not subject to annual ERISA Title I reporting that covers only:

• the owner of the entire business and the owner's spouse, or
• one or more partners and their spouses

A more-than-2% S corporation shareholder is treated as a partner for this purpose. A plan is not a one-participant plan if it benefits anyone else, such as an employee.

When you must file

The IRS one-participant 401(k) page states that a plan is generally required to file Form 5500-EZ if it has $250,000 or more in assets at the end of the year, and that plans with fewer assets may be exempt. The IRS CP214 notice page adds two important points:

• the threshold applies to assets alone or combined with other one-participant plans you maintain
• a return is required for the final plan year, whatever the assets

Track your plan balance at year end. Investment growth alone can push you over the threshold.

Due date for the 2026 plan year

The IRS Form 5500 corner says the due date is the last day of the seventh month after the plan year ends, which is July 31 for a calendar-year plan. For a 2026 calendar-year plan, that is July 31, 2027. You can request an extension using Form 5558.

How to file

• Electronically through the Department of Labor's EFAST2 system, using its web filing or an approved vendor.
• On paper to the IRS, if you are not subject to mandatory electronic filing.

The IRS explains that for plan years beginning on or after January 1, 2024, a filer required to file at least 10 returns of any type with the IRS during the calendar year must file Form 5500-EZ electronically. Information for one-participant plans filed through EFAST2 is not published online, according to the IRS.

What the form asks

Expect to provide:

• plan and employer identification details
• plan type and effective date
• plan assets and liabilities at the beginning and end of the year
• contributions and distributions
• participant information

Your plan provider's year-end statement contains most of the figures.

Missed filings

If you discover you should have filed in earlier years, act quickly. The IRS offers a penalty relief program for Form 5500-EZ late filers. The Department of Labor notes that late or delinquent one-participant plan filings cannot be submitted through EFAST2 and must be filed on paper with the IRS. Check the current program terms on IRS.gov before filing.

When the plan changes

• Hiring employees: if your plan begins to cover employees, it is no longer a one-participant plan and different reporting applies. See hiring your first employee.
• Terminating the plan: file a final return for the last plan year.
• Switching to a SEP: SEPs do not file Form 5500-EZ, but closing the 401(k) still requires a final return.

Practical routine

1. each January, check your plan balance at December 31
2. if over the threshold, or closing the plan, diary the July 31 deadline
3. gather the provider's year-end statement
4. file through EFAST2 or on paper
5. keep a copy of the return and confirmation

The guide to the solo 401(k) covers contributions and set-up, and the comparison of the SEP IRA and solo 401(k) helps if you are still choosing.

Keep a filing note

Record each year's plan assets and filing status in your retirement records, so you know at a glance when filing applies.

For the 2026 plan year, file Form 5500-EZ by July 31, 2027 for a calendar-year solo 401(k) if one-participant plan assets reach the $250,000 threshold or the plan is ending, file electronically if required, and use the IRS relief program for missed years.