Key Takeaways
- A one-participant 401(k) is a business retirement plan with ongoing rules, not a shortcut to unlimited tax savings.
- Employee deferrals and employer contributions have different limits and calculations.
- Check reporting duties and what changes if the business hires eligible employees.
A solo 401(k), also called a one-participant 401(k), can provide a retirement-saving route for a business owner without employees, or for the owner and spouse. Whether it fits depends on the business, eligible earnings, other retirement plans and the work required to maintain it. A large headline contribution limit does not establish how much you personally can put in.
1. Confirm who the plan must cover
The IRS one-participant plan guidance describes this as a traditional 401(k) covering an owner with no employees, or the owner and spouse. It is subject to the rules and requirements that apply to 401(k) plans. The product name used by a provider does not override those rules.
Before opening one, identify employees across the business and ask an appropriately qualified plan professional about eligibility and any related businesses. Hiring employees who satisfy the plan’s eligibility requirements changes the analysis: they must be included, and testing or other plan requirements may apply. Recheck when staffing changes instead of assuming the plan can always remain owner-only.
2. Separate the employee and employer calculations
The owner may contribute in two roles. Employee elective deferrals are limited by eligible compensation and the applicable annual deferral limit. Employer nonelective contributions have a separate calculation, with an overall contribution limit also applying. Age-related catch-up rules may be relevant, but they are not extra room available to every owner.
If you also participate in a 401(k) at another job, the personal elective-deferral limit is not duplicated simply because you have two plans. Coordinate the year’s deferrals. Do not assume that the largest advertised solo-plan total can be added to a full employee deferral elsewhere.
For a self-employed individual, the IRS requires a special earned-income calculation that accounts for one-half of self-employment tax and contributions for yourself. Gross business receipts, cash in a business account and eligible plan compensation are not interchangeable. Use the applicable IRS worksheets and qualified help rather than multiplying gross sales by a contribution percentage.
3. Check dates, tax treatment and provider terms
Before committing, confirm the plan-adoption date, election requirements, deposit deadlines and tax year with the provider and tax adviser. Deadlines and available options can depend on the business structure, contribution type and applicable rules. Avoid a blanket claim that every employee contribution has the same year-end deadline.
Ask which pre-tax, Roth or other contribution features the actual plan supports and how current tax rules apply. A feature permitted by law may still be absent from a provider’s document. Do not assume employer contributions must always be pre-tax, that every withdrawal is tax-free or that an IRA contribution is automatically deductible alongside this plan.
4. Review costs and administration
- Setup, annual account, investment and termination fees.
- The plan document, amendment service and who handles required filings.
- Available investments and their fees, liquidity and restrictions.
- Whether loans are permitted and their actual terms; borrowing is not an automatic low-cost benefit.
- How records and compliance will be handled if the business grows or closes.
No single account label establishes that a plan has no hidden costs, needs no administration or can hold an investment without tax or prohibited-transaction concerns. Understand the arrangement before moving money or signing documents.
5. Put reporting on the calendar
The IRS says a one-participant plan generally must file Form 5500-EZ if it has $250,000 or more in assets at year-end. Smaller plans may qualify for an exemption, but do not assume the threshold answers every filing situation. Consult the current instructions, including rules relevant to termination and electronic filing. The IRS Form 5500-EZ page identifies the annual reporting form; an old reference to Form 5500-SF is not a sufficient instruction.
Keep a written record of eligibility, the contribution calculation, elections, deposits, balances and filing responsibility. Compare the plan with other retirement-saving options and the cash your household needs before funding it. Starting or expanding a business solely to chase a tax limit can create costs and obligations that outweigh the benefit.
Official sources
Related reading
- Review 401(k) contributions, vesting and fees
- Calculate net side-hustle income
- Compare traditional and Roth IRAs
