For a full breakdown of IRA and Roth IRA rules, contribution limits, and conversion strategies, see the IRA and Roth IRA hub.
-nan Choosing between a SEP IRA and Solo 401(k) is one of the most consequential retirement decisions for self-employed individuals and freelancers. Both plans offer significant tax advantages and high contribution limits — far beyond what a standard IRA allows — but they work very differently in practice.
The short answer: if you earn under $300,000 and want to save the most possible, the Solo 401(k) typically wins. If simplicity is your priority, the SEP IRA is hard to beat. The tables below break down every scenario.
Quick Comparison
| Feature | SEP IRA | Solo 401(k) |
|---|---|---|
| Employee contributions | No | Yes ($23,500) |
| Employer contributions | Yes (up to 25%) | Yes (up to 25%) |
| 2025 total limit | $69,000 | $69,000 ($76,500 if 50+) |
| Roth option | No | Yes |
| Loan provision | No | Yes (up to $50K) |
| Catch-up contributions (50+) | No | Yes ($7,500) |
| Form 5500 required | No | Only if >$250K |
| Setup complexity | Simple | Moderate |
| Employees allowed | Yes (must include) | Only owner + spouse |
The biggest distinction: a SEP IRA only accepts employer contributions (up to 25% of net income), while a Solo 401(k) lets you contribute as both employee and employer. This “dual contribution” structure gives the Solo 401(k) a significant advantage at income levels below $300,000.
2025 Contribution Limits
SEP IRA Limits
| Factor | 2025 Limit |
|---|---|
| Maximum contribution | $69,000 |
| Percentage of compensation | 25% of net SE income* |
| Catch-up (50+) | None |
| Deadline | Tax filing deadline + extensions |
*Net SE income = Gross SE income - 1/2 SE tax - SEP contribution
Solo 401(k) Limits
| Factor | 2025 Limit |
|---|---|
| Employee contribution | $23,500 |
| Catch-up (50+) | +$7,500 = $31,000 |
| Employer contribution | 25% of net SE income* |
| Total maximum | $69,000 ($76,500 if 50+) |
| Deadline | Employee: Dec 31; Employer: Tax filing deadline |
Both plans share the same overall $69,000 cap, aligning with the total 401(k)/SEP limit set by the IRS. But if you’re over 50, the Solo 401(k) allows an extra $7,500 in catch-up contributions — a feature the SEP IRA lacks entirely. Compare these figures with standard 401(k) contribution limits for W-2 employees.
Contribution Comparison by Income
This is where the Solo 401(k) advantage becomes crystal clear. At lower and moderate incomes, the employee contribution component lets you shelter significantly more money from taxes.
At $50,000 Net Self-Employment Income
| Plan | Employee | Employer | Total |
|---|---|---|---|
| SEP IRA | $0 | $10,000 (20%)* | $10,000 |
| Solo 401(k) | $23,500 | $10,000 (20%)* | $33,500 |
Solo 401(k) advantage: $23,500 more
*Note: Employer contribution based on adjusted net SE income
At $50,000 of self-employment income, the Solo 401(k) lets you save more than 3x what a SEP IRA allows. That extra $23,500 in annual tax-advantaged savings compounds enormously over a career — at 7% growth, it’s an additional $2.4 million over 35 years.
At $100,000 Net Self-Employment Income
| Plan | Employee | Employer | Total |
|---|---|---|---|
| SEP IRA | $0 | $18,587 (20%)* | $18,587 |
| Solo 401(k) | $23,500 | $18,587 (20%)* | $42,087 |
Solo 401(k) advantage: $23,500 more
At $150,000 Net Self-Employment Income
| Plan | Employee | Employer | Total |
|---|---|---|---|
| SEP IRA | $0 | $27,881 (20%)* | $27,881 |
| Solo 401(k) | $23,500 | $27,881 (20%)* | $51,381 |
Solo 401(k) advantage: $23,500 more
At $300,000+ Net Self-Employment Income
| Plan | Employee | Employer | Total |
|---|---|---|---|
| SEP IRA | $0 | $69,000 (max) | $69,000 |
| Solo 401(k) | $23,500 | $45,500 | $69,000 |
At very high income, limits converge
This is the key crossover point. Once your income exceeds roughly $300,000, both plans hit the $69,000 ceiling. The Solo 401(k) still offers Roth and loan features, but the contribution amounts are identical. If simplicity matters and you earn over $300,000, the SEP IRA makes a strong case.
The Employer Contribution Calculation
Understanding the 25% Limit
The “25%” employer contribution is actually closer to 20% of net self-employment income after adjustments. This confuses many freelancers who expect to shelter a full quarter of their earnings. Here’s how the math actually works:
| Step | Calculation |
|---|---|
| Start with net SE income | $100,000 |
| Subtract 1/2 SE tax | -$7,065 |
| Adjusted income | $92,935 |
| × 25% | $23,233 max employer contribution |
Effective rate: ~20% of original net SE income
Quick Calculation
| Net SE Income | Approx. Max Employer Contribution |
|---|---|
| $50,000 | $9,294 |
| $75,000 | $13,940 |
| $100,000 | $18,587 |
| $150,000 | $27,881 |
| $200,000 | $37,175 |
| $250,000 | $46,468 |
| $300,000+ | $69,000 cap |
This calculation is identical for both SEP IRA and Solo 401(k) employer contributions. The difference is that the Solo 401(k) adds the $23,500 employee contribution on top. Understanding your marginal vs. effective tax rate helps determine the actual tax savings these contributions generate.
Which Plan to Choose
Choose SEP IRA If:
| Situation | Why SEP Works |
|---|---|
| You want simplicity | Easiest to set up and maintain |
| Income exceeds $300K | Same limits as Solo 401(k) |
| Have employees | Can include them (though costly) |
| Sporadic self-employment | Flexibility to not contribute some years |
| Don’t need loans | Simpler without loan provision |
| Already have Roth IRA for Roth option | SEP is traditional only |
Choose Solo 401(k) If:
| Situation | Why Solo 401(k) Works |
|---|---|
| Income under $300K | Higher contribution potential |
| Want Roth option | Roth Solo 401(k) available |
| Want loan access | Can borrow up to $50K |
| Over 50 | $7,500 catch-up contribution |
| Want mega backdoor Roth | After-tax contributions possible |
| Just you (or +spouse) | No other employees |
If you’re debating between these plans and a traditional employer-sponsored 401(k) vs. Roth IRA, remember that employer plans generally offer higher contribution limits. Self-employed plans are specifically designed to give you the same tax-advantaged savings options that W-2 employees enjoy through workplace plans. For an overview of all options, see our retirement account comparison.
Tax Treatment
Traditional Contributions
| Plan | Tax Treatment |
|---|---|
| SEP IRA | Tax-deductible now, taxed at withdrawal |
| Solo 401(k) Traditional | Tax-deductible now, taxed at withdrawal |
Both plans reduce your taxable income dollar-for-dollar on contributions. If you’re in the 24% federal tax bracket and contribute $40,000, you save $9,600 in federal income taxes that year. This makes self-employed retirement contributions one of the most powerful tax deductions available.
Roth Option
| Plan | Roth Available? | Tax Treatment |
|---|---|---|
| SEP IRA | No | — |
| Solo 401(k) | Yes | After-tax now, tax-free at withdrawal |
The Roth Solo 401(k) is uniquely valuable for self-employed individuals who expect higher tax rates in retirement or want tax diversification. Unlike a Roth IRA, the Roth Solo 401(k) has no income limits — even high earners can contribute. This is essentially a backdoor Roth strategy built into the plan.
Tax Savings Example: $100K Income, $25K Contribution
| Tax Rate | Annual Tax Savings |
|---|---|
| 22% bracket | $5,500 |
| 24% bracket | $6,000 |
| 32% bracket | $8,000 |
Setup and Maintenance
SEP IRA
| Task | What’s Involved |
|---|---|
| Setup | Open SEP IRA at any brokerage |
| Forms | IRS Form 5305-SEP (keep in records) |
| Annual filing | None |
| Contribution deadline | Tax filing deadline + extensions |
| Cost | Usually free |
A SEP IRA can be opened in minutes online. You don’t even need to file the form with the IRS — just keep it in your records. This simplicity is the SEP IRA’s biggest selling point.
Solo 401(k)
| Task | What’s Involved |
|---|---|
| Setup | Apply with brokerage (more forms) |
| Forms | Plan document, adoption agreement |
| Annual filing | Form 5500-EZ if assets exceed $250K |
| Contribution deadline | Employee: Dec 31; Employer: Tax deadline |
| Cost | Usually free, some providers charge |
The Solo 401(k) requires more upfront paperwork and has a hard deadline: you must establish the plan by December 31 to make employee contributions for that tax year. SEP IRAs can be established as late as your tax filing deadline (including extensions), making them the go-to choice for last-minute retirement savings.
Providers Comparison
| Provider | SEP IRA | Solo 401(k) | Roth Solo 401(k) | Loans |
|---|---|---|---|---|
| Fidelity | ✓ | ✓ | ✓ | No |
| Vanguard | ✓ | ✓ | ✓ | No |
| Schwab | ✓ | ✓ | ✓ | No |
| E*TRADE | ✓ | ✓ | ✓ | Yes |
| TD Ameritrade | ✓ | ✓ | ✓ | Yes |
| Guideline | ✓ | ✓ | ✓ | Yes |
All major brokerages offer both plans with no account fees. The main differentiator is loan availability and investment options. If you want access to low-cost index funds, Fidelity, Vanguard, and Schwab all offer broad selection with minimal expense ratios.
Special Situations
Multiple Jobs (W-2 + Self-Employment)
| Scenario | Consideration |
|---|---|
| Have 401(k) at W-2 job | Employee contribution limit is combined |
| Example: $15K to employer 401(k) | Can only add $8,500 to Solo 401(k) as employee |
| Employer contributions | Still full 25% available for self-employment |
This is critical: the $23,500 employee contribution limit applies across all your 401(k) plans combined. If you already contribute $15,000 to your employer’s 401(k) or 403(b), you can only put $8,500 into a Solo 401(k) as an employee contribution. However, the employer contribution (25% of net SE income) is separate and fully available. With a SEP IRA, there’s no conflict since it’s all employer contributions.
Spouse as Employee
| Plan | Spouse Treatment |
|---|---|
| SEP IRA | Must include if employee (at same %) |
| Solo 401(k) | Can include spouse, doubling household limit |
Spouse in Solo 401(k)
| If Both Earn $100K | Individual | Combined |
|---|---|---|
| Employee contribution | $23,500 each | $47,000 |
| Employer contribution | $18,587 each | $37,174 |
| Total | $42,087 each | $84,174 |
A spousal Solo 401(k) is one of the most powerful retirement savings strategies for married self-employed couples. Sheltering $84,174 per year in tax-advantaged accounts accelerates retirement savings dramatically, especially when combined with Roth conversions in lower-income years.
Transitioning Between Plans
| From | To | Considerations |
|---|---|---|
| SEP IRA | Solo 401(k) | Can roll over SEP to Solo 401(k) |
| Solo 401(k) | SEP IRA | Can roll over, but lose loan ability |
| Either | New employer 401(k) | Can roll over |
Rolling a SEP IRA into a Solo 401(k) (or vice versa) is generally tax-free and straightforward. One tactical reason to consolidate: if you want to execute a backdoor Roth IRA conversion, having pre-tax IRA balances (including SEP IRAs) triggers the pro-rata rule. Rolling SEP IRA funds into a Solo 401(k) clears the path for clean backdoor Roth conversions.
Contribution Strategies
Maximize Tax Savings
| Income Level | Strategy |
|---|---|
| Under $100K | Solo 401(k) for higher contributions |
| $100K-$200K | Solo 401(k), consider Roth portion |
| Over $200K | Either plan approaches max |
At lower income levels, maximizing your Solo 401(k) contribution can significantly reduce your effective tax rate. A freelancer earning $75,000 who contributes $37,440 to a Solo 401(k) cuts their taxable self-employment income roughly in half — potentially dropping from the 22% to the 12% federal bracket.
Roth vs Traditional
| Choose Roth If | Choose Traditional If |
|---|---|
| Tax rates rising | Tax rates falling in retirement |
| Lower income now | Higher income now |
| Want tax diversification | Need deduction now |
| Young (long growth horizon) | Closer to retirement |
With the 2026 tax changes potentially raising rates when current Tax Cuts and Jobs Act provisions expire, Roth contributions may be especially attractive right now for those who can afford to forgo the current deduction.
Year-End Rush
| Plan | December Deadline | Tax Filing Deadline |
|---|---|---|
| SEP IRA | None | Full contribution |
| Solo 401(k) | Employee portion | Employer portion |
If it’s late December: Solo 401(k) must be established by Dec 31 for employee contributions; SEP IRA can be set up until tax filing deadline. This timing flexibility makes the SEP IRA ideal for those who don’t plan ahead — you can open one in April and still make a full contribution for the prior year.
Key Takeaways
-
Solo 401(k) allows higher contributions at lower income — $23,500 employee + 25% employer
-
SEP IRA is simpler — Easier setup, less paperwork, later deadline
-
Roth option only with Solo 401(k) — Tax-free growth potential with no income limits
-
Loans only with Solo 401(k) — Access up to $50K if needed
-
High earners ($300K+) see same limits — Both cap at $69K
-
Solo 401(k) must be open by Dec 31 — SEP can wait until tax deadline
For more on workplace retirement plans, see the Workplace Retirement Plans hub.
The content on Wealthvieu is for informational purposes only and should not be considered financial, tax, or investment advice. Consult a qualified professional before making financial decisions. Full disclaimer · Editorial policy