Form 5500-EZ vs Form 5500-SF for a Solo 401(k)
Which annual return a one-participant plan files, when Form 5500-SF takes over, and where Solo 5500 Desk stops.
Summary
Our answer: a Solo 401(k) that covers only the owner (or partners) and spouses files Form 5500-EZ, on paper with the IRS or electronically through EFAST2; the Department of Labor says one-participant plans can no longer use Form 5500-SF. Form 5500-SF is the short electronic return for small ERISA plans, generally under 100 participants at the start of the year, with secure investments and an audit waiver. Example: an LLC whose plan covers only the owner and spouse files 5500-EZ once assets pass $250,000; the same LLC after covering one eligible employee leaves the EZ lane and, if eligible, files 5500-SF. Solo 5500 Desk prepares Form 5500-EZ only.
One-participant plan = Form 5500-EZ (paper or EFAST2). Form 5500-SF = small ERISA plan with covered employees, electronic only.
| 5500-EZ | One-participant or foreign planOwners/partners and their spouses only; paper with the IRS or electronic through EFAST2. |
|---|---|
| 5500-SF | Small ERISA plan, fewer than 100 participantsOr up to 120 if it filed as a small plan the prior year (80-120 rule). |
| 5500-SF filing | EFAST2 onlyNo paper Form 5500-SF by mail (2025 instructions). |
| Due date (both) | Last day of the 7th month after plan year endJuly 31 for a calendar-year plan; Form 5558 adds up to 2 1/2 months. |
| Product boundary | 5500-EZ packet onlyNo Form 5500-SF, no Form 8955-SSA, no plan with covered employees. |
Our verdict
Count who the plan covers before you choose a form. Only the owner (or partners) and spouses: Form 5500-EZ, and the only question is whether you must file it at all ($250,000 threshold, final year) and whether it must be electronic (10 or more IRS returns). Any covered employee: you are no longer in the EZ lane, and no Solo 401(k) packet fits.
Who this page is for, and who it is not for
For: owners of a Solo 401(k) unsure which annual return applies, especially after hiring. Not for: plans with employees, multiemployer or pooled employer plans, defined benefit plans that need Schedule SB, and anyone needing a TPA to administer the plan.
Side by side
Checked against the Department of Labor's Form 5500 page and the 2025 Form 5500-SF instructions on October 28, 2026.
| Form 5500-EZ | Form 5500-SF | |
|---|---|---|
| Plan covered | One-participant plan (owners/partners and spouses) or foreign plan | Small ERISA pension or welfare plan with covered employees |
| Size test | None; filing required above $250,000 of plan assets (or in the final year) | Fewer than 100 participants at the start of the year, or up to 120 under the 80-120 rule |
| Other conditions | Not subject to ERISA annual reporting (ERISA section 104(a)) | Secure investments with a readily determinable fair value, audit waiver, no employer securities, not multiemployer or pooled employer plan |
| How to file | Paper with the IRS, or electronically through EFAST2 (mandatory at 10 or more IRS returns) | Electronically through EFAST2 only |
| Due date | Last day of the 7th month after plan year end; Form 5558 extension | Same |
| Solo 5500 Desk | Packet prepared | Not supported |
Sources: DOL Form 5500 page; 2025 Instructions for Form 5500-SF; IRS About Form 5500-EZ.
When to stop
Stop if you are unsure whether the plan is still one-participant, if the plan covers an employee, if you need an amended or late filing, or if a prior year was filed on a different 5500-series form. Those are questions for the official instructions or a qualified plan professional.
Common questions
Can a Solo 401(k) use Form 5500-SF instead?
No longer. The Department of Labor's Form 5500 page says Form 5500-SF can no longer be used to file one-participant plan and foreign plan returns electronically; those plans file Form 5500-EZ. A one-participant plan that wants to file electronically submits the 5500-EZ itself through EFAST2.
When does a Solo 401(k) have to switch to Form 5500-SF?
When the plan stops being a one-participant plan, typically because it covers a common-law employee. It then becomes an ERISA plan; if it meets all the small-plan conditions (generally fewer than 100 participants, eligible secure investments, audit waiver), it can file Form 5500-SF, otherwise Form 5500.
Is the deadline different?
No. Both are due by the last day of the 7th month after the plan year ends (July 31 for a calendar-year plan), and Form 5558 filed by that date gives one extension of up to 2 1/2 months.
What is the 80-120 participant rule?
A plan that filed as a small plan the prior year may keep filing as a small plan, and use Form 5500-SF if otherwise eligible, as long as it covers no more than 120 participants at the start of the year.
Do I attach Form 8955-SSA to Form 5500-SF?
No. The 2025 Form 5500-SF instructions say not to attach Form 8955-SSA, which is filed separately for separated participants with deferred vested benefits.
Related guides
Do I need to file Form 5500-EZ for my Solo 401(k)?
The direct filing test for one-participant plans: asset threshold, final year, deadline, and filing method.
Solo 401(k) $250,000 threshold for Form 5500-EZ
How the IRS $250,000 one-participant plan asset threshold works for Solo 401(k) Form 5500-EZ filing.
Final Solo 401(k) plan year: when Form 5500-EZ still matters
Why a terminating one-participant plan can still have a Form 5500-EZ filing even below the normal asset threshold.
Official sources for this guide
Last reviewed: .