Form 5500 for Solo 401(k): When Your Plan Balance Triggers a Filing Requirement

What is it

• An annual filing required once a Solo 401(k) exceeds a certain asset level
• Reports basic information about the plan to the IRS and Department of Labor
• Filed as Form 5500-EZ (or 5500-SF in some cases)
• Required once the plan crosses the balance threshold
  

Who it affects

• Business owners with a Solo 401(k) (no full-time employees)
• Applies to sole proprietors, partnerships, and owner-only corporations
• Triggered when plan assets exceed $250,000 at year-end
• Also required when the plan is terminated, regardless of balance
  

How it works

• Filing is required for the year the plan balance is over $250,000
• Due July 31 (calendar-year plans), with extension to October 15 (Form 5558)
• Reports total plan assets, contributions, distributions, and basic plan information
• No audit required (unlike large employer plans)
  

Key threshold

• $250,000 plan balance at year-end
• Below this level: No filing required
• Above this level: Annual filing required going forward
• Filing continues each year until plan balance drops below threshold or plan is closed
  

Penalties (if not filed)

• IRS: Up to $250 per day (max $150,000 per return)
• DOL penalties may also apply in certain cases
• Late filings can often be corrected using IRS/DOL relief programs
  

Example

A sole proprietor has a Solo 401(k) worth $265,000 at the end of 2025. They must file Form 5500-EZ by July 31, 2026 (or extend to October 15). Even if contributions stop, they must continue filing annually while the balance remains above $250,000.