SEP-IRA vs. Solo 401(k) is one of the first decisions many self-employed business owners face when they are ready to start saving seriously for retirement. Both plans allow significantly higher contributions than a Traditional or Roth IRA, and both are relatively simple to open. However, the two plans differ in important ways, including how much you can contribute, whether a Roth option is available, and how much paperwork is involved. Understanding these differences can help freelancers, consultants, and small business owners choose the plan that best fits their income and long-term goals.
Why the Choice Matters for Self-Employed Savers
Unlike employees who participate in a workplace 401(k), self-employed individuals must set up and fund their own retirement plan. The plan you choose affects how much you can shelter from taxes each year, how flexible your contributions can be from year to year, and how much administrative work falls on your shoulders. For many small business owners, the difference between a SEP-IRA and a Solo 401(k) can amount to tens of thousands of dollars in additional retirement savings over a working career.
SEP-IRA: Simple to Set Up, Employer Contributions Only
A Simplified Employee Pension IRA, commonly known as a SEP-IRA, allows a business owner to contribute on behalf of themselves as the “employer.” For 2026, contributions cannot exceed the lesser of 25 percent of compensation or $72,000, and compensation used in the calculation is capped at $360,000, according to the Internal Revenue Service. There are no separate employee elective deferrals and no catch-up contributions for those age 50 and older.
The appeal of a SEP-IRA lies in its simplicity. There is minimal paperwork, no annual filing requirement in most cases, and contributions can be made as late as the business tax filing deadline, including extensions. This flexibility makes it attractive to business owners with variable income who want to decide how much to contribute after they know their annual results. The tradeoff is that a SEP-IRA does not offer a Roth option and does not permit loans against the account balance.
Solo 401(k): Higher Potential Contributions for Owner-Only Businesses
A Solo 401(k), also called an individual 401(k), is designed for business owners with no employees other than a spouse. It allows contributions in two capacities. As the “employee,” the owner may defer up to $24,500 in 2026, with an additional catch-up contribution of $8,000 for those age 50 to 59 or 64 and older, or $11,250 for those age 60 to 63. As the “employer,” the owner may also contribute up to 25 percent of net self-employment compensation. Combined employee and employer contributions cannot exceed $72,000 for 2026, or up to $80,000 with catch-up contributions included, subject to compensation limits.
Because the employee deferral applies regardless of the 25 percent compensation limit, a Solo 401(k) often allows a business owner with modest income to contribute more than a SEP-IRA would allow at the same income level. Many Solo 401(k) plans also offer a Roth option, meaning contributions can be made after tax in exchange for tax-free qualified withdrawals in retirement. Some providers also permit participant loans, which is not available with a SEP-IRA.
Comparing SEP-IRA and Solo 401(k) at a Glance
| Feature | SEP-IRA | Solo 401(k) |
|---|---|---|
| 2026 maximum contribution | Lesser of 25% of compensation or $72,000 | Up to $72,000 ($80,000+ with catch-up) |
| Employee elective deferral | Not available | Up to $24,500 (plus catch-up if eligible) |
| Roth option | No | Often available |
| Participant loans | No | Sometimes, depending on provider |
| Annual filing (Form 5500-EZ) | Generally not required | Required once assets reach $250,000 |
| Best suited for | Owners who want simplicity and late-funding flexibility | Owner-only businesses seeking to maximize contributions on modest income |
What About a SIMPLE IRA?
Business owners who plan to hire employees down the road should also be aware of the SIMPLE IRA, a third option intended for small employers. For 2026, employees may defer up to $17,000, or $18,100 for employers with 25 or fewer employees who adopt the enhanced limit, with additional catch-up contributions available for those 50 and older. The SIMPLE IRA plan rules require the employer to make either a matching or a fixed nonelective contribution each year, which makes it less flexible than a SEP-IRA but easier to administer than a typical 401(k) once staff are added.
How to Decide Between a SEP-IRA and a Solo 401(k)
The right choice generally depends on income level, whether the business has or will have employees, and how much administrative complexity the owner is willing to manage. A few general patterns are worth considering:
- Owner-only businesses with moderate income often benefit from a Solo 401(k), because the employee deferral allows meaningful contributions even in years when net earnings are relatively modest.
- Owners who want maximum simplicity and the ability to decide on contributions after year-end results are known may prefer a SEP-IRA.
- Business owners who plan to add employees should weigh the cost of extending a SEP-IRA to future staff against the structured, shared-cost approach of a SIMPLE IRA.
- Those who value a Roth savings option or the ability to borrow against their balance will generally find more flexibility in a Solo 401(k).
A Quick Self-Check
Does a Solo 401(k) make sense for my business?
A Solo 401(k) is generally worth considering if the business has no full-time employees other than a spouse, if net self-employment income is under roughly $150,000 to $200,000 (where the employee deferral makes a meaningful difference in total contributions), and if the owner wants access to a Roth option or the ability to take a plan loan. If any of these do not apply, a SEP-IRA or SIMPLE IRA may be a better fit, and a conversation with a financial professional can help clarify the tradeoffs.
Contribution Deadlines and Compensation Rules Still Apply
Regardless of which plan is chosen, contributions are still governed by IRS compensation limits, and the total combined limit across employer and employee contributions applies across all defined contribution plans an individual maintains. The IRS reviews these thresholds annually as part of its cost-of-living adjustments, and the 2026 retirement plan limit announcement reflects the most recent increases. Business owners should also confirm plan-specific deadlines with their provider, since a Solo 401(k) generally must be established by December 31 of the tax year to accept employee deferrals for that year, while a SEP-IRA can often be opened and funded up until the business tax filing deadline, including extensions.
Bringing It Together
Choosing between a SEP-IRA and a Solo 401(k) is not a one-size-fits-all decision. Income level, future hiring plans, and the desire for features like Roth contributions or plan loans all factor into which structure will serve a business owner best over time. Because retirement plan selection also interacts with broader tax planning, cash flow needs, and overall investment strategy, it is often worthwhile to review the decision with a professional who can look at the full financial picture.
If you are a business owner or self-employed professional weighing a SEP-IRA, Solo 401(k), or SIMPLE IRA, we invite you to schedule a free 30-minute call with Rooney Wealth Management to discuss which approach may fit your situation.
Rooney Wealth Management LLC is an investment adviser registered with the state of California. This article is for educational purposes only and is not tax, legal, or investment advice. Please consult your tax or financial professional regarding your specific situation.
