SEP IRA vs Solo 401k: Key Differences and 2026 Limits

A SEP IRA and a Solo 401k both allow self-employed individuals to save for retirement with valuable tax advantages. However, they differ significantly in how contributions work, who can participate, how much administration they require, and what features they offer.

The primary difference between a SEP IRA and a Solo 401(k) is the contribution structure. A SEP IRA accepts employer contributions, while a Solo 401(k) allows an eligible business owner to contribute in two roles: as both an employee and an employer.

This distinction can make a Solo 401(k) particularly attractive for a business owner who wants to contribute a larger percentage of moderate self-employment income. A SEP IRA may be more suitable when simplicity and minimal administration are the main priorities.

SEP IRA vs Solo 401(k) at a Glance

Contribution limits depend on compensation, business structure, other retirement plans, and applicable IRS calculations. The stated limits are not automatically available to every participant.

What Is a SEP IRA?

A Simplified Employee Pension Individual Retirement Arrangement, commonly called a SEP IRA, is an employer-sponsored retirement arrangement designed for self-employed individuals and businesses.

Freelancers, independent contractors, sole proprietors, partnerships, corporations, and businesses with employees can establish one.

A traditional SEP IRA is funded through employer contributions. Employees generally do not make salary-deferral contributions to it as they would to a 401(k). A self-employed person is treated as the employer when making contributions for themselves.

SEP IRA contributions are generally discretionary. A business can contribute in one year and reduce or skip its contribution in another year. However, if the business contributes for its owner, it generally must contribute the same percentage of compensation for every eligible employee covered by the plan.

That requirement can make a SEP IRA expensive for a business with multiple eligible employees.

What Is a Solo 401(k)?

A Solo 401(k), also called an individual 401(k), one-participant 401(k), or self-employed 401(k), is intended for a business owner with no eligible common-law employees other than the owner’s spouse.

The business owner participates in two capacities:

• As an employee, the owner can make elective salary-deferral contributions.
• As the employer, the business can make an additional employer contribution.

Having two contribution sources is one of the plan’s biggest advantages. It may allow a self-employed person to reach a higher contribution at a lower level of business income than would be possible with a SEP IRA.

A Solo 401(k) follows many of the same tax rules as a conventional workplace 401(k). Our comparison of Roth and traditional 401(k) contributions explains how paying taxes now differs from deferring them until retirement.

SEP IRA vs Solo 401(k) Contribution Limits for 2026

According to the IRS, the basic employee elective-deferral limit for a 401(k) is $24,500 in 2026. The defined-contribution plan limit is $72,000, up from $70,000 in 2025. The IRS publishes these inflation-adjusted retirement limits annually.

SEP IRA contribution limit

SEP IRA contributions generally cannot exceed the lesser of:

• 25% of an employee’s eligible compensation; or
• $72,000 for 2026.

The calculation is different for a self-employed person. Because the contribution reduces net earnings used in the calculation, the practical maximum is generally equivalent to approximately 20% of adjusted net earnings from self-employment—not a simple 25% of Schedule C profit.

Business owners should use the worksheet in IRS Publication 560 or consult a qualified tax professional before calculating the maximum contribution.

SEP IRA contributions do not qualify for the regular age-50 catch-up contribution because they are employer contributions rather than employee elective deferrals.

Solo 401(k) contribution limit

An eligible Solo 401(k) participant may contribute in two roles.

Employee contribution: Up to $24,500 for 2026, limited by eligible compensation and any employee deferrals made to another 401(k), 403(b), or similar plan.

Employer contribution: The business may make an additional contribution based on eligible compensation and business structure.

Combined employee and employer contributions generally cannot exceed $72,000 for 2026, excluding eligible catch-up contributions.

Participants age 50 or older can generally contribute an additional $8,000 in 2026. Participants who are ages 60 through 63 during 2026 may qualify for the higher $11,250 catch-up limit.

With sufficient eligible compensation, that could raise the total to:

• $80,000 for a participant eligible for the standard catch-up; or
• $83,250 for an eligible participant age 60 through 63.

These limits apply per person, not automatically per account. Contributions to another employer’s plan can affect the amount available for a Solo 401(k).

Contribution Example

Suppose a 40-year-old sole proprietor has $80,000 in net self-employment earnings before considering retirement-plan contributions and related adjustments.

With a SEP IRA, the contribution would be based only on the employer contribution formula. It would not necessarily equal 25% of the stated $80,000 because a special self-employed calculation applies.

With a Solo 401(k), the owner may first make an employee deferral and then add an employer contribution. The two-part structure could produce a higher total contribution at this income level.

The exact result will depend on deductible self-employment tax, adjusted net earnings, business structure, and contributions made to other retirement plans.

Eligibility Differences

Who can establish a SEP IRA?

A SEP IRA may be established by:

• A sole proprietor
• An independent contractor
• A partnership
• An LLC
• An S corporation
• A C corporation
• A business with eligible employees

A business does not need to generate a specific minimum amount of revenue to establish the plan, but contributions require eligible compensation.

Employers generally must cover employees who meet the plan’s eligibility requirements. A business may use less restrictive eligibility rules, but it cannot selectively exclude employees who meet the adopted requirements.

Who can establish a Solo 401(k)?

A Solo 401(k) is generally available to a self-employed person or business owner who has no eligible common-law employees other than a spouse.

Having part-time workers does not always immediately make the owner ineligible. However, employees who meet applicable participation requirements may eventually have to be included. Once eligible employees must participate, the arrangement can become a conventional small-business 401(k) with additional testing and administration.

Employers should not assume that calling a worker an independent contractor automatically excludes that person. Worker classification depends on the actual working relationship.

Which Plan Allows Larger Contributions?

A Solo 401(k) frequently allows larger contributions when income is moderate because the owner can make an employee deferral before adding the employer contribution.

As income increases, both plans may eventually reach the same $72,000 basic annual ceiling.

Therefore:

• A Solo 401(k) often has the advantage at lower or moderate income levels.
• The difference may shrink at sufficiently high compensation.
• A participant eligible for catch-up contributions can potentially contribute more through a Solo 401(k).
• A SEP IRA may still be preferable when ease of operation matters more than maximizing contributions.

Tax Treatment and Roth Options

Traditional SEP IRA contributions are generally deductible by the employer and grow tax-deferred. Distributions are usually taxable as ordinary income.

The SECURE 2.0 Act permits Roth treatment for certain SEP contributions when the plan and financial institution support it. However, availability and provider implementation can vary.

A Solo 401(k) may offer both traditional and Roth employee contributions, depending on the plan document and provider. Traditional contributions generally reduce current taxable income, while qualified Roth withdrawals may be tax-free after applicable requirements are met.

Employer Roth contributions may also be available under newer rules if supported by the plan.

Choosing between pretax and Roth contributions depends on current income, expected future tax rates, cash flow, and retirement strategy—not simply the size of the deduction.

Investment Choices and Fees

Both accounts may hold investments such as:

• Stocks
• Bonds
• Mutual funds
• Exchange-traded funds
• Money market funds
• Certificates of deposit

The specific investment menu depends on the financial institution or plan provider.

A SEP IRA is usually straightforward to open at a brokerage and may have few administrative charges. A Solo 401(k) may involve setup fees, annual maintenance charges, recordkeeping expenses, or transaction costs.

Investors should compare:

• Account administration fees
• Fund expense ratios
• Trading charges
• Roth availability
• Loan provisions
• Rollover options
• Customer support
• Range of investments

Remember that a retirement account is a tax structure rather than an investment itself. The distinction between a tax-advantaged account and an ordinary investment account is also explained in our guide to IRA and brokerage account differences.

Can You Borrow From the Account?

A SEP IRA cannot offer participant loans. Taking money from it generally counts as a distribution and may result in income tax and an additional early-distribution tax if no exception applies.

A Solo 401(k) may permit participant loans if its plan document includes a loan provision. Federal limits and repayment requirements apply. Failing to repay according to the rules can cause the unpaid amount to be treated as a taxable distribution.

A loan should not be the main reason for choosing a retirement plan. Borrowing can interrupt long-term compounding and place retirement savings at risk.

Administrative and Filing Requirements

SEP IRA administration

A SEP IRA is generally easier to administer because it ordinarily does not require annual Form 5500 filing, nondiscrimination testing, or separate employee salary-deferral records.

The employer must still:

• Adopt a valid written arrangement
• Give required information to eligible employees
• Apply its contribution formula consistently
• Deposit contributions into each participant’s SEP IRA
• Maintain accurate records

Solo 401(k) administration

A Solo 401(k) requires a formal plan document and more recordkeeping.

A participant may need to file Form 5500-EZ when total one-participant plan assets exceed $250,000 at the end of the plan year. A final return may also be required when the plan is terminated, regardless of asset size.

Contribution elections, deposits, plan amendments, and deadlines must be handled correctly. Rules may differ for sole proprietors and incorporated businesses, especially when salary deferrals are made through payroll.

Setup and Contribution Deadlines

A SEP IRA can generally be established and funded by the employer’s federal tax-return deadline, including extensions, for the applicable tax year.

Solo 401(k) deadlines are more complicated. They can depend on:

• When the plan was established
• Whether the business is incorporated
• Whether the contribution is an employee deferral or employer contribution
• Whether the owner has employees
• Whether the plan is being opened for the first time

Do not wait until the tax-filing deadline to assume every type of Solo 401(k) contribution remains available. Confirm the relevant deadline with the plan provider or a qualified tax adviser before the end of the year.

Advantages and Disadvantages

SEP IRA advantages

• Simple to establish and maintain
• Generally no annual IRS return
• Flexible employer contributions
• Available to businesses with employees
• Potentially high contribution ceiling
• Broad investment selection at many brokerages

SEP IRA disadvantages

• No regular employee elective deferrals
• No catch-up contribution
• No participant loans
• Contributions for eligible employees may become expensive
• Roth availability may be limited by provider support

Solo 401(k) advantages

• Employee and employer contributions
• Potentially larger contributions at moderate income levels
• Age-based catch-up contributions
• Traditional and Roth options may be available
• Participant loans may be permitted
• A spouse working in the business may participate

Solo 401(k) disadvantages

• More administrative responsibility
• Potential Form 5500-EZ filing
• Generally unsuitable for a business with eligible non-spouse employees
• Provider and plan fees may be higher
• Contribution calculations and deadlines can be complex

SEP IRA vs Solo 401(k): Which Is Better?

A Solo 401(k) may be better when:

• You have no eligible employees other than your spouse.
• You want to maximize contributions at a moderate income level.
• You want to make Roth employee contributions.
• You qualify for catch-up contributions.
• You are comfortable with additional administration.

A SEP IRA may be better when:

• You want the simplest available plan.
• You may hire or already have eligible employees.
• You do not need employee deferrals or catch-up contributions.
• Your business income fluctuates.
• You prefer to avoid annual 401(k) filing requirements.

Neither plan is universally better. The right choice depends on eligible compensation, age, employees, business structure, other workplace plans, desired tax treatment, and administrative preferences.

Can You Have Both a SEP IRA and a Solo 401(k)?

It may be possible to maintain both arrangements, but opening two plans does not necessarily double the contribution limit.

When the same business sponsors both plans, employer contributions may be aggregated under applicable annual limits. Employee deferrals are also subject to an individual annual limit across relevant plans.

Controlled-group and affiliated-business rules can further affect eligibility and limits. Establishing both plans should therefore be reviewed with a tax or retirement-plan professional.

Frequently Asked Questions

Is a SEP IRA better than a Solo 401(k)?

A SEP IRA may be better for simplicity or for a business with employees. A Solo 401(k) may be better for an owner-only business seeking employee deferrals, Roth options, catch-up contributions, or potentially larger contributions at moderate income.

Can a Solo 401(k) contribution reduce taxable income?

Traditional employee deferrals and deductible employer contributions may reduce current taxable income, subject to applicable limits and business tax rules. Roth contributions do not provide the same current federal income-tax deduction.

Can an S corporation owner open either plan?

Yes. An eligible S corporation can establish either type of plan. Contributions for an owner-employee are generally based on W-2 compensation rather than shareholder distributions.

Does a SEP IRA allow Roth contributions?

Federal law now permits Roth treatment for certain SEP contributions, but the plan and financial institution must support the feature. Traditional pretax SEP arrangements remain more widely available.

Can a spouse participate in a Solo 401(k)?

Yes, if the spouse performs genuine work for the business and receives eligible compensation. Each spouse may have a separate participant account under the plan and may contribute subject to individual compensation and annual limits.

Final Thoughts

The central difference in the SEP IRA vs Solo 401(k) comparison is contribution flexibility.

A SEP IRA provides a relatively simple employer-funded retirement arrangement. A Solo 401(k) provides an owner-only business with both employee and employer contribution opportunities, potential catch-up contributions, and additional plan features.

For many self-employed individuals without employees, the Solo 401(k) offers greater contribution flexibility. For business owners who prioritize simplicity or need to cover eligible employees, the SEP IRA may be the more practical choice.

Before establishing either plan, verify your contribution calculation, eligibility, deadlines, and tax treatment with the plan provider or a qualified financial or tax professional.

This article is for educational purposes only and does not constitute tax, legal, investment, or financial advice.