Form 5500-EZ is an IRS tax form used by Solo 401k account holders to report plan information. It’s required for self-employed individuals or small business owners with no full-time employees (other than a spouse) when plan assets exceed $250,000 at the end of the plan year. Filing ensures compliance with IRS rules and is simpler than forms required for larger plans. The form is typically due by the last day of the seventh month after the plan year ends (e.g., July 31 for a calendar-year plan).