TL;DR: The SEP IRA vs Solo 401k comparison comes down to your business structure, employees, contribution goals, and preferred level of administration. Both offer tax advantages and higher contribution limits than traditional IRAs, but they provide different ways to save.
- A SEP IRA uses employer contributions and offers relatively simple administration and flexibility when business income changes.
- A Solo 401k allows eligible business owners to contribute as both an employee and employer, potentially increasing savings opportunities.
- SEP IRAs can cover employees, but employers generally must contribute the same percentage of compensation for eligible workers.
- Solo 401ks are generally limited to businesses with no eligible employees other than a spouse and may offer Roth and catch-up contributions.
- Actual contribution amounts depend on factors such as compensation, age, business structure, and other retirement accounts.
SEP IRA vs Solo 401k is a common comparison for self-employed workers and business owners who want to save more for retirement. Both accounts offer tax advantages and much higher contribution limits than a traditional IRA, but they handle contributions, employees, and administration differently.
Here’s what you need to know before picking one.
What Is a SEP IRA?
A Simplified Employee Pension, or SEP IRA, is a retirement plan that lets business owners contribute toward retirement for themselves and their employees. Freelancers, independent contractors, and small business owners often use SEP IRAs because they’re relatively simple to set up and manage.
Unlike a typical workplace 401k, a traditional SEP IRA relies on employer contributions rather than employee salary deferrals. You also get flexibility because you don’t have to contribute every year, which can help if your business income changes from one year to the next.
Employees can change the equation. Under SEP IRA rules, an employer who contributes for themselves generally has to contribute the same percentage of compensation for each eligible employee. The IRS SEP contribution rules explain the limits and requirements in more detail.
What Is a Solo 401K?
A Solo 401k is a 401k plan for a business owner with no employees other than a spouse. You may also hear people call it an individual 401k, one-participant 401k, Solo-k, or Uni-k.
The biggest difference comes from how you contribute. As the business owner, you can contribute in two roles: employee and employer. This structure can give you more opportunities to put money away, especially when your business earns enough to support larger contributions.
A Solo 401k can also allow catch-up contributions once you reach the eligible age, and some plans offer Roth contributions. The tradeoff is more paperwork and administration than you’d typically face with a SEP IRA. You can review the IRS rules for one-participant 401(k) plans for more detail.
SEP IRA vs Solo 401K: What’s the Difference?
The main difference between a SEP IRA and a Solo 401k comes down to how you make contributions and who works for your business. With a SEP IRA, the employer makes the contribution. If you have eligible employees, you generally need to contribute the same percentage of compensation for them as you contribute for yourself.
A Solo 401k only works if you have no eligible employees other than your spouse, but it lets you contribute as both an employee and an employer.
Here’s a quick breakdown for a SEP IRA:
- Simpler administration and flexible employer contributions.
- Can cover a business with employees.
- May require contributions for eligible employees when the owner contributes.
Now, let’s look at a Solo 401K:
- Employee plus employer contributions and potential catch-up contributions.
- Generally limited to an owner-only business or an owner and spouse.
- Can offer Roth features, depending on the plan.
Your income, workforce, and savings goals can make one structure more useful than the other.
SEP IRA Contribution Limits
The SEP IRA contribution limits allow an employer to contribute up to the lesser of 25% of an employee’s eligible compensation or $72,000. Self-employed workers have to calculate their limit differently because the IRS bases the calculation on net earnings from self-employment after certain adjustments, so you can’t simply take 25% of gross business revenue.
SEP contributions also give business owners flexibility. You can contribute less during a lean year or make no contribution at all, which can matter when your business income changes.
Retirement choices also work best when they fit into your broader financial planning for small business owners, especially if your income, taxes, and business expenses change from year to year.
Solo 401K Contribution Limits
Solo 401k contribution limits work differently because you can contribute as both an employee and employer. For 2026, you can make employee elective deferrals of up to $24,500 or 100% of eligible compensation, whichever is lower.
The business can then make an employer contribution. Your combined regular contributions generally can’t exceed $72,000 for 2026 or 100% of compensation, whichever applies.
If you’re age 50 or older, your plan may also allow an $8,000 catch-up contribution in 2026. Participants ages 60 through 63 can qualify for a higher $11,250 catch-up limit.
These rules can make a Solo 401(k) useful for an owner who wants to save aggressively without needing as much business income to reach a higher contribution amount.
When Does a SEP IRA Make Sense?
A SEP IRA may fit your business if you value simple administration and want control over how much you contribute each year. It may also work well if your income changes from year to year and you don’t need employee salary deferrals.
A SEP IRA may make sense if:
- Your business income varies.
- You want fewer administrative requirements.
- You don’t need employee salary deferrals.
- You want the option to contribute for employees.
If you have employees, calculate the potential cost before setting up the plan. Contributing a certain percentage for yourself can require you to give eligible employees the same percentage.
When Does a Solo 401K Make Sense?
A Solo 401(k) may fit if you work for yourself and have no eligible employees other than your spouse. It can give you more contribution options and may appeal to business owners who want to put away more at lower income levels.
You may find it useful if:
- You want to contribute as both employee and employer.
- You want access to catch-up contributions.
- You want a plan with a possible Roth option.
- You want more ways to increase retirement contributions.
Keep future hiring plans in mind. Adding eligible employees can change your plan requirements because a Solo 401k can’t remain an owner-only plan once qualifying employees participate.
SEP IRA vs Solo 401K: How Do You Choose?
Start with your business and your actual numbers. Ask yourself whether you have employees, how much the business earns, how much you want to contribute, if Roth or catch-up contributions matter, and if you expect to hire employees soon.
The maximum contribution shown on paper doesn’t tell you how much you can actually contribute. Your compensation, business structure, other retirement accounts, age, and tax situation can all affect the calculation.
Your retirement account should also support your larger strategy. A broader retirement planning approach can help you consider taxes, investments, income needs, and long-term goals alongside annual contribution limits.
A SEP IRA keeps administration relatively simple, while a Solo 401k gives an owner-only business more ways to contribute. Compare the actual numbers for your situation before deciding which is best for you.
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A Roth conversion may not be suitable for your situation. The primary goal in converting retirement assets into a Roth IRA is to reduce the future tax liability on the distributions you take in retirement, or on the distributions of your beneficiaries. The information provided is to help you determine whether or not a Roth IRA conversion may be appropriate for your particular circumstances. Please review your retirement savings, tax, and legacy planning strategies with your legal/tax advisor to be sure a Roth IRA conversion fits into your planning strategies.
Stewart Willis is the founder and president of Asset Preservation Wealth & Tax, a financial planning firm in Phoenix, Arizona. Investment advisory services offered through Foundations Investment Advisors, LLC, an SEC registered investment adviser.
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