Solo 401(k) vs. SEP IRA: Which Retirement Plan Fits a Self-Employed Business Owner?
If you work for yourself, the solo 401k vs SEP IRA question is one of the first retirement decisions you will face. Without an employer plan, it is up to you to choose how you save, how much you can put away, and how the account fits with the rest of your finances. Both plans can offer meaningful tax advantages. They just work differently.
Common questions come up fast: Which plan lets me save more? What if I hire employees later? Can I make Roth contributions? How much paperwork is involved? This guide compares the two side by side in plain language so you can have a more informed conversation about your own situation.
What Is a Solo 401(k)?
A solo 401(k), sometimes called an individual 401(k) or one-participant 401(k), is a retirement plan designed for a business owner with no employees other than a spouse who works in the business.
How Contributions Work
Employee contributions: As the owner, you can contribute as the "employee" of your business, up to the annual employee deferral limit set by the IRS.
Employer contributions: Your business can also contribute as the "employer," generally based on a percentage of your compensation or net self-employment earnings.
Combined total: The two types together are subject to an overall annual limit, which the IRS updates periodically.
Features to Know
Roth option: Many solo 401(k) plans allow Roth employee contributions, which are made after tax and may grow tax free if rules are met.
Catch-up contributions: Owners above a certain age may be able to add catch-up contributions.
Loans: Some plans permit loans, though not all providers offer this feature.
What Is a SEP IRA?
A SEP IRA, or Simplified Employee Pension, is an employer-funded retirement plan. It is often popular with sole proprietors and small businesses because it is easy to set up and maintain.
How Contributions Work
Employer contributions only: Contributions are made by the business, generally as a percentage of compensation, up to an annual IRS limit.
No employee deferrals: There is no separate "employee" contribution like in a 401(k).
Flexible year to year: You generally do not have to contribute every year, which can help when income is uneven.
Features to Know
Simple paperwork: Setup is usually straightforward, and ongoing administration tends to be light.
Employee coverage rules: If you have eligible employees, you generally must contribute the same percentage of pay for them as you do for yourself.
Roth availability: Recent law changes have opened the door to Roth SEP contributions, but availability depends on the provider. Check current IRS guidance and your custodian's options.
Solo 401k vs SEP IRA: Key Differences Side by Side
When people search for the best retirement plan for self-employed owners, they usually want to know how these plans compare on a few practical points.
Contribution Potential
Solo 401(k): Because you can contribute as both employee and employer, some owners may be able to save more at lower income levels.
SEP IRA: Contributions are based only on a percentage of compensation, so the amount you can contribute is closely tied to how much you earn.
Employees
Solo 401(k): Generally only works if you have no eligible employees other than a spouse.
SEP IRA: Can cover employees, but you must contribute for eligible staff on the same basis as yourself.
Administration
Solo 401(k): Once plan assets reach a certain level, an annual IRS filing (Form 5500 EZ) may be required.
SEP IRA: Generally no annual IRS filing for the plan itself.
Deadlines
Solo 401(k): Plan setup and employee deferral elections often have earlier deadlines, so timing matters.
SEP IRA: You can often establish and fund a SEP up to your tax filing deadline, including extensions.
Rules and limits can change, so check current IRS guidance or work with a tax professional before deciding.
Questions to Ask Before You Choose
Choosing a self-employed retirement plan is less about which plan is "better" and more about which plan fits your business and goals.
How Much Do You Want to Save?
If your goal is to save as much as possible, compare how each plan's contribution formula works at your expected income. The answer may change as your income grows.
Do You Plan to Hire?
If you expect to add employees, a SEP IRA or a different type of plan may make more sense over time. A solo 401(k) may need to be replaced or converted once you have eligible staff.
Do You Want Roth Savings?
If having a mix of pre-tax and Roth money matters to you, review which Roth features each provider offers. Having tax diversity in retirement can create more flexibility later.
How Much Administration Will You Handle?
A SEP IRA tends to be simpler. A solo 401(k) can offer more features but may come with a bit more paperwork.
How This Fits Into Your Bigger Financial Picture
Your retirement plan is one piece of a broader strategy. For business owners, it connects with cash flow, taxes, and long-term goals like a future sale or transition.
Tax Planning
Pre-tax contributions: Can lower your taxable income in the year you contribute.
Roth contributions: Can create tax-free income later if rules are met.
Coordinating both: Some owners consider a blend to manage taxes now and in retirement.
Investment Approach
Once money is in the plan, how it is invested matters too. Our insights on tax loss harvesting and why investment returns alone don't determine financial success explore how decisions beyond returns can shape outcomes.
Do Not Wait Too Long
Deadlines can sneak up, especially for solo 401(k) setup. Read The Cost of Waiting to see why delaying financial decisions can cost more over time.
How Auric Capital Partners Can Help
Auric Capital Partners is located in Aliso Viejo, California. The firm describes its approach as bringing "clarity, structure, partnership" and "disciplined thinking and genuine connection to every part of your financial life."
Auric offers financial planning, retirement income planning, tax minimization strategies, estate planning, multigenerational planning, and investment advisory services. You can view the full list on our Services page.
Who Auric Serves
Business owners navigating liquidity events and retirement
Executives and professionals with equity compensation
Families experiencing major life transitions
Retirees
The right-fit client who values "follow-through, honesty, and trust"
As the firm puts it, Auric works with "founders, professionals, and families who have built something meaningful. People who do not need another pitch, but a real partner." Learn more about us.
Let's Connect About Your Retirement Plan
If you are weighing a solo 401(k) against a SEP IRA, we are here to help you think it through. No scripts, no pressure. Schedule a conversation with Auric Capital Partners, and we will respond with thoughtful, personalized support.
Frequently Asked Questions
Is a solo 401k or SEP IRA better for self-employed people?
Neither is better for everyone. A solo 401(k) may allow higher contributions at some income levels and often offers Roth options, while a SEP IRA is simpler and can cover employees. The right fit depends on your income, staff, and goals.
Can I have both a solo 401k and a SEP IRA?
In some cases it may be possible, but contribution limits are generally shared or coordinated across plans for the same business. Rules are detailed, so check current IRS guidance or ask a tax professional.
What happens to my solo 401k if I hire employees?
Once you have eligible employees, a solo 401(k) generally no longer fits. You may need to move to a different plan that covers your staff.
When is the deadline to open a SEP IRA?
A SEP IRA can often be opened and funded up to your business tax filing deadline, including extensions. Confirm current deadlines with IRS guidance.
Can I make Roth contributions to a SEP IRA?
Recent law changes allow Roth SEP contributions, but not every custodian offers them yet. Ask your provider and review current IRS guidance.
Does a solo 401k require an annual tax filing?
A solo 401(k) may require an annual Form 5500 EZ filing once plan assets pass a certain threshold. Check the current threshold with the IRS.
This content is for educational and informational purposes only and should not be considered investment, tax, or legal advice. It is not a recommendation to buy or sell any security or to adopt any particular investment strategy. Investing involves risk, including the possible loss of principal. Past performance is no guarantee of future results, and no strategy can guarantee a profit or protect against loss. Please consult with a qualified professional about your individual situation. Registered Representative of Sanctuary Securities Inc. and Investment Advisor Representative of Sanctuary Advisors, LLC. Securities offered through Sanctuary Securities, Inc., Member FINRA, SIPC. Advisory services offered through Sanctuary Advisors, LLC., a SEC Registered Investment Adviser. Auric Capital Partners is a DBA of Sanctuary Securities, Inc. and Sanctuary Advisors, LLC.
