SEP IRA vs Solo 401(k) For Self Employed

SEP IRA vs. Solo 401(k) for Self-Employed: A Comprehensive Comparison Guide

If you work for yourself, choosing the right retirement plan is one of the most important financial decisions you can make. Two of the most popular options for self-employed individuals are the SEP IRA (Simplified Employee Pension) and the Solo 401(k), sometimes called an Individual 401(k). Both offer significant tax advantages and high contribution limits, but they work in fundamentally different ways.

This guide breaks down how each plan works, walks through real contribution calculations, and highlights the trade-offs so you can have a more informed conversation with your financial advisor.

What Is a SEP IRA?

A SEP IRA is a retirement account that allows self-employed individuals and small business owners to make tax-deductible contributions on behalf of themselves (and eligible employees, if any). It was designed to be simple to set up and maintain, which is one reason it remains popular.

Key features of a SEP IRA include:

Contributions are made only by the employer (you, as the self-employed person). There is no employee elective deferral component.
For 2025 and 2026, the maximum contribution is the lesser of 25% of net self-employment income or $70,000 (2025) or $70,000 (2025 limit, with the 2026 limit subject to IRS cost-of-living adjustments).
Contributions are tax-deductible, reducing your taxable income for the year.
All contributions are made on a pre-tax basis. There is no Roth option for SEP IRAs under current law.
No annual IRS filing requirements (such as Form 5500) for the plan itself.
Easy to open at most brokerages with minimal paperwork.

What Is a Solo 401(k)?

A Solo 401(k) is a 401(k) plan designed for self-employed individuals with no full-time employees other than a spouse. It mirrors the structure of a traditional employer-sponsored 401(k) but is tailored for a business of one (or two, if your spouse works in the business).

Key features of a Solo 401(k) include:

Two contribution components: an employee elective deferral and an employer profit-sharing contribution.
For 2025, the employee deferral limit is $23,500 (with a $7,500 catch-up contribution for those aged 50 and older). The 2026 employee deferral limit is $23,500, subject to IRS announcement of any adjustment.
The total combined contribution limit (employee plus employer) is $70,000 for 2025 (or $77,500 with the standard catch-up for those 50 and older). Note: Under SECURE 2.0, those aged 60 to 63 may be eligible for an enhanced catch-up contribution of $11,250 instead of $7,500, bringing their total potential limit even higher.
Roth contributions are available for the employee deferral portion, allowing after-tax contributions that grow tax-free.
Loan provisions may be available, depending on the plan document, allowing you to borrow from your own retirement savings.
Requires more administrative setup and, once plan assets exceed $250,000, an annual Form 5500-EZ filing with the IRS.

Side-by-Side Comparison

Contribution Structure

This is the single biggest structural difference between the two plans. A SEP IRA allows only employer contributions, calculated as a percentage of your net self-employment income. A Solo 401(k) allows both employee deferrals (a flat dollar amount up to the annual limit) and employer profit-sharing contributions (a percentage of income).

This distinction matters most when your income is moderate. At lower income levels, the Solo 401(k) typically allows you to contribute significantly more because of the employee deferral component. At very high income levels, the two plans may converge on similar maximum contribution amounts.

Roth Option

If tax diversification is part of your long-term planning strategy, the Solo 401(k) has a clear structural advantage. You can designate some or all of your employee deferral as Roth contributions. With a SEP IRA, all contributions are pre-tax. There is no Roth SEP IRA option.

Having both pre-tax and Roth money in retirement can provide flexibility for managing your tax bracket during withdrawals. However, Roth contributions do not reduce your current-year taxable income, which is a trade-off to consider.

Administrative Complexity

A SEP IRA is one of the simplest retirement plans to establish and maintain. You can typically open one online in under 30 minutes, there are no annual IRS filings, and contribution calculations are straightforward.

A Solo 401(k) requires adopting a formal plan document, and some providers charge annual fees. Once your plan assets exceed $250,000, you must file Form 5500-EZ with the IRS each year. If you fail to file, the IRS can assess penalties. For some self-employed individuals, this added complexity is a worthwhile trade-off. For others, the simplicity of the SEP IRA is more appropriate.

Loan Provisions

A Solo 401(k) plan can include a loan provision, which allows you to borrow up to $50,000 or 50% of your vested account balance (whichever is less) and repay it with interest over five years. A SEP IRA does not permit loans. Borrowing from retirement savings carries risks, including the possibility of taxes and penalties if you cannot repay, but having the option may provide a financial safety net for some self-employed individuals.

Worked Example: Contribution Comparison at $80,000 Net Income

Let’s walk through a realistic scenario. Suppose you are a 40-year-old freelance consultant with $80,000 in net self-employment income (after deducting the employer-equivalent portion of self-employment tax).

SEP IRA Calculation

For a sole proprietor, the effective contribution rate to a SEP IRA is approximately 20% of net self-employment income (this accounts for the fact that the contribution itself reduces the income it is based on, making the effective rate 20% rather than 25%).

$80,000 x 20% = $16,000 maximum SEP IRA contribution

Solo 401(k) Calculation

With a Solo 401(k), you can make two types of contributions:

Employee deferral: up to $23,500 (2025 limit). However, since your income is $80,000, you can defer up to $23,500.
Employer profit-sharing: approximately 20% of net self-employment income = $80,000 x 20% = $16,000.
Total: $23,500 + $16,000 = $39,500

In this scenario, the Solo 401(k) allows you to contribute $23,500 more than the SEP IRA. That is a substantial difference. Over time, this extra contribution capacity can compound significantly.

The Compounding Impact

Let’s illustrate what this difference could mean over 25 years (from age 40 to 65), assuming a hypothetical 7% average annual return before fees. The 7% figure is often used as a rough historical average for a diversified portfolio, though actual returns vary year to year and are never guaranteed.

If you contribute $16,000 per year (SEP IRA maximum at this income level):

Future value = $16,000 x [(1.07^25 – 1) / 0.07] = $16,000 x 63.249 = approximately $1,011,984

If you contribute $39,500 per year (Solo 401(k) maximum at this income level):

Future value = $39,500 x 63.249 = approximately $2,498,336

The difference of roughly $1.49 million illustrates why contribution capacity matters. Of course, many self-employed individuals cannot afford to contribute the maximum every year, and actual investment returns will vary. This example is purely illustrative.

When a SEP IRA May Be the Better Fit

You value simplicity above all else. If you want the easiest possible setup with minimal paperwork, the SEP IRA is hard to beat.
Your income is very high. At high income levels (roughly $350,000 and above in net self-employment income), the maximum contribution amounts for both plans converge. The SEP IRA’s simplicity becomes more attractive when the contribution difference narrows or disappears.
You have employees or plan to hire. SEP IRAs can cover employees, though you must contribute the same percentage of compensation for all eligible employees as you contribute for yourself. A Solo 401(k), by contrast, is only available if you have no full-time employees other than your spouse.
You are just getting started. If you are newly self-employed and want to open a retirement account quickly with minimal friction, a SEP IRA can be established and funded up to your tax filing deadline (including extensions).

When a Solo 401(k) May Be the Better Fit

Your net self-employment income is under approximately $200,000. At these income levels, the employee deferral component of the Solo 401(k) allows you to save significantly more than a SEP IRA.
You want Roth contribution access. If building a tax-free retirement income stream is part of your long-term plan, only the Solo 401(k) offers this option.
You want the ability to borrow from your plan. The loan provision, while carrying risks, provides a flexibility that SEP IRAs do not offer.
You are age 50 or older. Catch-up contributions of $7,500 (or $11,250 for ages 60 to 63 under SECURE 2.0) can substantially increase your annual contribution ceiling.
You are a sole proprietor or have no employees other than your spouse. The Solo 401(k) is designed specifically for this situation.

Important Trade-Offs to Consider

The Employee Question

If your business grows and you hire full-time employees (generally those working 1,000 or more hours per year), you would need to convert your Solo 401(k) to a standard 401(k) plan, which involves additional administrative requirements and costs. With a SEP IRA, you can continue the plan but must contribute the same percentage for all eligible employees, which can become expensive.

Contribution Deadlines

Both plans allow contributions up to your tax filing deadline, including extensions. A SEP IRA can also be established by that deadline. However, a Solo 401(k) must generally be established (the plan document adopted) by December 31 of the tax year for which you want to make employee deferral contributions. Employer profit-sharing contributions can still be made up to the filing deadline. This timing requirement is important to plan for.

Required Minimum Distributions (RMDs)

Both SEP IRAs and pre-tax Solo 401(k) accounts are subject to required minimum distributions beginning at age 73 (under current law, with the age increasing to 75 starting in 2033 under SECURE 2.0). Roth contributions within a Solo 401(k) are also currently subject to RMD rules, though recent legislation has made changes that may eliminate RMDs for designated Roth accounts in employer plans. Consult a tax professional for the most current rules.

Backdoor Roth IRA Considerations

If you use a strategy involving after-tax traditional IRA contributions converted to a Roth IRA (sometimes called a “backdoor Roth”), having a SEP IRA can complicate this process. The IRS pro-rata rule treats all of your traditional IRA balances (including SEP IRA balances) as one pool when calculating the taxable portion of a conversion. A Solo 401(k) is not an IRA and is not subject to this rule, which may preserve your ability to execute this strategy cleanly. Discuss this with a qualified tax professional.

Can You Have Both?

Yes, it is technically possible to maintain both a SEP IRA and a Solo 401(k). However, the total combined contributions across both plans cannot exceed the annual limit ($70,000 for 2025, or more with catch-up contributions). In most cases, choosing one plan and maximizing it is simpler and more practical. Having both adds complexity without necessarily increasing your total contribution capacity.

A Note on Social Security

Regardless of which plan you choose, your self-employment income (after self-employment tax deductions but before retirement plan contributions) is used to calculate your Social Security earnings record. According to the Social Security Administration, the average monthly retirement benefit as of early 2025 is approximately $1,976. For many self-employed individuals, personal retirement savings will need to supplement Social Security benefits substantially. This makes maximizing your retirement plan contributions especially important.

Making Your Decision

There is no universally correct answer. The right plan depends on your specific income level, tax situation, desire for Roth access, tolerance for administrative complexity, plans for hiring employees, and overall retirement strategy. Many self-employed individuals benefit from reviewing their choice periodically as their business and income evolve.

A qualified financial advisor or tax professional can help you model your specific situation and determine which plan structure aligns with your goals.

This article was created with the assistance of AI and reviewed for accuracy.

Data Sources

Disclaimer: RetireGrader is not a financial advisor or fiduciary. This content is for educational purposes only. Consult a qualified financial advisor before making retirement planning decisions. Tax laws and contribution limits are subject to change. The examples and calculations shown are hypothetical and do not represent any specific investment outcome.