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Solo 401(k) vs. SEP IRA: which is better for freelancers in 2026?
For most one-person businesses with no employees, the Solo 401(k) wins on contribution math, Roth flexibility, and backdoor Roth compatibility. Here's the 2026 framework.
If you're a freelancer, sole proprietor, or single-member LLC with no W-2 employees, this is one of the highest-leverage tax decisions you'll make. The right retirement account can shelter $74,500 per year of self-employment income from federal tax in 2026.
The short answer: a Solo 401(k) beats a SEP IRA in almost every realistic scenario. The SEP IRA wins on simplicity and last-minute setup; the Solo 401(k) wins on everything else — contribution math at moderate incomes, Roth availability, and keeping the backdoor Roth IRA path open.
The 2026 numbers, side by side
| Feature | Solo 401(k) | SEP IRA |
|---|---|---|
| 2026 total cap | $74,500 | $74,500 |
| Employee deferral | $24,500 | Not allowed |
| Employer contribution | Up to 25% net SE income | Up to 25% net SE income |
| Catch-up (50+) | +$8,000 | None |
| Super catch-up (60–63) | +$11,250 | None |
| Roth option | Yes — supported widely | Yes — limited provider support |
| Backdoor Roth IRA compatible? | Yes | No (pro-rata problem) |
| Loans allowed | Yes (up to $50K) | No |
| Plan setup deadline | Dec 31 of tax year | Tax-filing deadline + extensions |
| Annual filing | Form 5500-EZ if assets > $250K | None |
2026 limits from IR-2025-111 (Nov 13, 2025).
The contribution math that decides it
Both plans cap employer contributions at 25% of net self-employment income (effectively ~20% of gross SE income after the half-SE-tax deduction). The Solo 401(k) adds the $24,500 employee deferral on top of that. That deferral is the whole game at low and middle incomes.
Here's what that looks like across realistic income levels:
| Net SE income | SEP IRA cap | Solo 401(k) cap | Difference |
|---|---|---|---|
| $30,000 | ~$5,575 | ~$30,075 | +$24,500 |
| $50,000 | ~$9,290 | ~$33,790 | +$24,500 |
| $100,000 | ~$18,587 | ~$43,087 | +$24,500 |
| $200,000 | ~$37,174 | ~$61,674 | +$24,500 |
| $300,000+ | $74,500 | $74,500 | $0 |
Net SE income = gross SE income − half of SE tax − other above-the-line adjustments. Real-world numbers vary; use Schwab's or Fidelity's Solo 401(k) calculator for your specific situation.
At every income below ~$300K, the Solo 401(k) shelters $24,500 more per year.Over 20 years at 7%, that's the difference between $1.0M and $0.0 in extra tax-deferred growth.
The backdoor Roth blocker (why this matters most)
Anyone earning above the Roth IRA income phase-out (~$165K single / ~$246K MFJ in 2026) must use the backdoor Roth IRA to get money into a Roth. The mechanic: contribute to a non-deductible Traditional IRA, then convert to Roth.
The pro-rata rule wrecks this if you have a SEP IRA. The IRS treats ALL your IRA balances — Traditional, SEP, SIMPLE — as one pool when computing the taxable portion of any Roth conversion. So a $50,000 SEP IRA balance turns a clean $7,500 backdoor conversion into a mostly-taxed event:
- Total IRA balance: $50,000 SEP + $7,500 non-deductible Trad = $57,500
- Non-deductible fraction: $7,500 ÷ $57,500 = 13.0%
- Of the $7,500 you convert: only 13.0% ($978) is tax-free
- The other $6,522 is taxed at your ordinary federal rate
The Solo 401(k) is not an IRA. SEP balances rolled into a Solo 401(k) drop out of the pro-rata calculation. For high earners, opening a Solo 401(k) and rolling the SEP into it is often a multi-thousand-dollar unlock per year.
When the SEP IRA is still the right answer
- You realized in March that you missed last year's plan. SEP IRAs can still be opened AND funded for the prior tax year up to the filing deadline + extensions. Solo 401(k)s must be established by Dec 31.
- You expect to hire W-2 employees soon. Once you have employees, both plans get expensive (you must contribute proportionally for everyone). SEPs are slightly simpler to administer in the short term.
- You hate paperwork. SEP IRAs are one-page Form 5305-SEP and no annual reporting. Solo 401(k)s require Form 5500-EZ once assets cross $250K.
- You already have a 401(k) at a W-2 day job and want a small additional shelter. You can't double-dip employee deferrals — your $24,500 is shared across both 401(k)s. If you've already maxed the deferral at your day job, the SEP IRA gives you a clean way to shelter additional self-employment income.
The Roth angle
Solo 401(k) Roth is now standard. Fidelity, Schwab, and E*TRADE all offer Roth Solo 401(k)s at no cost. You can split the $24,500 deferral between pre-tax and Roth however you want.
SEP IRA Roth is technically allowed under SECURE 2.0 but rare in practice. Most SEP IRA providers haven't built support yet. The mechanics — pre-tax employer money mixed with post-tax employee Roth in the same account — are still being worked out.
If you want flexibility between current-year deduction and future-tax-free Roth, the Solo 401(k) is the clear choice. See Roth vs. Traditional IRA for the decision framework.
The mega backdoor Roth angle
Some Solo 401(k) plans support after-tax employee contributions with in-plan Roth conversion— the "mega backdoor Roth" mechanic. This lets you convert any unused space between your employer/employee total ($X) and the $74,500 §415(c) cap straight into Roth.
Default Fidelity, Schwab, and E*TRADE Solo 401(k)s do NOT support this — you need a custom-document Solo 401(k) (Mysolo401k, MySolo401k.net, or similar). The annual cost is ~$500–$1,000 setup + $150/year, but for a high earner the tax shelter can be worth tens of thousands.
SEP IRAs have no mega backdoor path at all. See mega backdoor Roth guide for full mechanics.
How to open one
The three brokerages worth using for a default Solo 401(k):
Fidelity and Schwab Solo 401(k)s are free, support pre-tax and Roth, and have clean online interfaces. Vanguard's Solo 401(k) is also free but charges $25/year per mutual fund (can be waived); their SEP IRA is more frictionless if you choose that route.
The bottom line
One-person business, no W-2 employees: Solo 401(k) almost every time. More tax shelter at low and middle incomes, Roth flexibility, backdoor Roth IRA stays clean.
SEP IRA wins only on simplicity and last-minute setup.If you're filing your 2025 return in April 2026 and realize you never opened a retirement account, the SEP IRA is your only legal path back. Open it, fund it, and then open a Solo 401(k) for 2026 and roll the SEP into it once the dust settles.
Related reading
- 401(k) vs. IRA: which first — the broader account-priority decision.
- Backdoor Roth IRA guide — why the SEP IRA blocks it.
- Mega backdoor Roth guide — for Solo 401(k) holders with high income.
- SECURE 2.0 changes for 2026 — the new Roth-SEP and Roth-SIMPLE rules.
- How much to contribute to your 401(k) — once you have the plan, here's how to fill it.
- When to hire a CPA — when the Solo 401(k) administrative overhead is worth professional help.
Frequently asked questions
- What's the 2026 contribution limit for a Solo 401(k)?
- $74,500 total — the same overall §415(c) defined-contribution limit that applies to any 401(k). That's the employee elective deferral up to $24,500 plus employer profit-sharing up to 25% of net self-employment income, capped at $74,500 combined. Add $8,000 catch-up if you're 50+, or $11,250 if you're 60–63 (SECURE 2.0 super catch-up). Source: IR-2025-111.
- What's the 2026 contribution limit for a SEP IRA?
- Up to 25% of net self-employment income, capped at the §415(c) limit of $74,500. There's no employee deferral component — every dollar comes from the 'employer' side, so you need substantially more income to max out a SEP than a Solo 401(k).
- Which lets me contribute more on a smaller income?
- The Solo 401(k), by a lot. On $50K net self-employment income, a SEP IRA caps your contribution around $9,294 (the 25% rule applied to net SE after the half-SE-tax deduction). A Solo 401(k) lets you contribute the same employer side PLUS the full $24,500 employee deferral on top — total around $33,800. The Solo 401(k) is the better choice for anyone earning under ~$300K.
- Why does the SEP IRA block the backdoor Roth IRA?
- The IRS aggregates all your traditional, SEP, and SIMPLE IRA balances when you do a backdoor Roth conversion under the pro-rata rule. If you have a $50K SEP IRA balance, only a small fraction of your $7,500 backdoor conversion is treated as tax-free — most of it gets taxed at your ordinary rate. The Solo 401(k) is not an IRA, so it doesn't count toward the pro-rata calculation. Backdoor Roth stays clean.
- Can a Solo 401(k) have a Roth option?
- Yes. Most major providers (Fidelity, Schwab, E*TRADE) now offer Roth Solo 401(k) plans at no cost. SEP IRAs are now allowed to have a Roth contribution feature under SECURE 2.0, but provider support is limited and the rules around employer pre-tax + employee Roth are still being worked out. Solo 401(k) Roth is the cleaner path.
- What's the deadline to open and fund?
- Solo 401(k): the plan must be ESTABLISHED by Dec 31 of the tax year (employer contributions can still be funded by the tax-filing deadline). SEP IRA: both establishment and funding deadlines are the tax-filing deadline including extensions (typically Oct 15). The SEP IRA wins for last-minute setup.