# Solo 401(k) vs. SEP-IRA: Which One Fits? URL: https://elevatedtaxstrategies.com/tax-planning/solo-401k-vs-sep-ira/ Markdown: https://elevatedtaxstrategies.com/tax-planning/solo-401k-vs-sep-ira.md Category: Tax Planning Published: 2026-03-10 Author: Ramon Liriano Jr. > Side-by-side comparison of Solo 401(k) and SEP-IRA for self-employed business owners. Contribution limits, paperwork, Roth options. ## TLDR For most self-employed owners, the **Solo 401(k) is the better choice**: higher contribution limit, Roth option, no setup ongoing cost, allows loans. The **SEP-IRA wins on simplicity only**: you can fund it the day before you file taxes and skip the year-end deadline that Solo 401(k) requires. Both let you contribute roughly $72K/yr at higher income levels in 2026, but the Solo 401(k) gets there with employee + employer split, while SEP-IRA is employer-only at 25% of net SE income. In this guide, you'll learn: - Understand the contribution-cap landscape for self-employed owners (Traditional IRA leaves 90%+ on the table) - Get the full Solo 401(k) mechanics, $24,500 employee deferral + 25% employer + catch-up + Roth + loans - Get the full SEP-IRA mechanics: employer-only, 25% of net SE income, tax-deadline funding, no Roth - See the side-by-side comparison table to pick the right vehicle for your situation - Recognize when SEP-IRA wins (missed Dec 31 Solo 401(k) deadline, employees, top-of-range with no Roth need) ## Why this comparison matters Self-employed owners (sole proprietors, single-member LLCs, S-corp owners) face a 2026 contribution-cap landscape that's wildly different from W-2 employees: - W-2 employee 401(k) limit: $24,500 employee deferral + $8,000 catch-up (50+) - Solo self-employed via Solo 401(k): up to ~$72K combined employee + employer - Solo self-employed via SEP-IRA: up to ~$72K via employer-only contribution Most self-employed owners default to a Traditional IRA ($7K limit) and leave 90%+ of their available contribution capacity on the table. The Solo 401(k) or SEP-IRA closes that gap. ## Solo 401(k): the deep version **Structure:** A 401(k) plan where the only participants are the business owner (and optionally a spouse). The owner wears two hats, employee + employer. **Contribution mechanics (2026):** - **Employee deferral**: up to $24,500 ($32,500 with catch-up if 50+), can be Roth or Traditional - **Employer contribution**: up to 25% of net self-employment income (after self-employment tax adjustment), Traditional only - **Combined cap**: $72,000 ($80,500 with catch-up) - **Spouse working in business**: spouse can contribute their own employee + employer share, effectively doubling the household capacity **Setup:** File Form 5500-EZ once balance exceeds $250K (annually thereafter). Initial plan document via brokerage (Fidelity, Schwab, E\*TRADE all offer free Solo 401(k)). Setup time: ~1 hour. Ongoing cost: $0 at most brokerages. **Roth feature:** Employee deferral can go to Roth Solo 401(k). Big advantage over SEP-IRA. Lets you split contribution between tax-deferred (employer side) and tax-free at retirement (employee Roth side). **Loans:** Solo 401(k) allows participant loans up to 50% of balance / $50K max. SEP-IRA does not. **Timing:** Plan must be established by **December 31** of the tax year to make employee contributions for that year. Employer contributions can be funded up to the tax-filing deadline (including extensions). ## SEP-IRA: the deep version **Structure:** Simplified Employee Pension IRA. Employer-only contribution into an IRA owned by each participant. **Contribution mechanics (2026):** - **Employer contribution only**: up to 25% of net self-employment income (after SE tax adjustment), capped at $72,000 - **No employee deferral:** entire contribution is employer-side - **No catch-up provision:** unlike 401(k), age 50+ doesn't add to the limit - **All employees must be included:** if you have non-spouse employees, you must contribute the same percentage for all eligible employees **Setup:** Open an SEP-IRA at any brokerage. ~15 minutes. No plan document required. **Roth feature:** SEP-IRA does NOT have a Roth option (as of 2026, the SECURE 2.0 Roth-SEP provision is technically available but most brokerages haven't implemented it). **Loans:** Not allowed. **Timing:** Can be opened and funded up to the tax-filing deadline (including extensions). For someone who files in October on an extension, this means you can establish and fund a SEP-IRA up to October 15 for the prior year. **Solo 401(k) doesn't allow this:** plan must exist by Dec 31. ## Side-by-side comparison **Solo 401(k) vs. SEP-IRA (2026)** | | Solo 401(k) | SEP-IRA | | --- | --- | --- | | Combined contribution limit (2026) | $72K / $80.5K w/ catch-up | $72K | | Employee deferral | $24,500 / $32.5K w/ catch-up | None | | Roth option | Yes (employee side) | No (effectively) | | Loans allowed | Yes, up to $50K | No | | Plan setup time | ~1 hour | ~15 minutes | | Form 5500-EZ filing | Required at $250K+ balance | None | | Plan must exist by | Dec 31 | Tax-filing deadline (incl. extensions) | | Catch-up contribution (50+) | $8,000 (employee side only) | None | ## When Solo 401(k) wins For most self-employed owners, this is the right answer: - **You want Roth contributions.** Solo 401(k) employee Roth gives you tax-free withdrawals in retirement on up to $24,500/yr. - **You're under 25% of net SE income at full Solo 401(k) capacity.** For a moderate-income solo ($60K-150K net), the Solo 401(k)'s $24,500 employee deferral is huge relative to what you could fund via SEP-IRA's 25%-of-net rule. - **You want flexibility on contribution timing/amount.** Each year you can dial employee + employer contributions independently. - **You might need a loan.** Solo 401(k) loan provision is the only retirement vehicle that lets you borrow from your own balance. - **You plan to roll a 401(k) from a former employer.** Solo 401(k) can accept rollover; SEP-IRA generally cannot accept former-employer 401(k) rollovers. ## When SEP-IRA wins Narrower: - **You're funding for a tax year that already ended and missed the Dec 31 Solo 401(k) deadline.** SEP-IRA can be opened and funded up to your tax-filing deadline (incl. extensions). This is the single most-common SEP-IRA scenario for ETS clients. - **You have employees and want to avoid 401(k) administration complexity.** SEP-IRA's all-employees-proportional rule is simpler than 401(k) non-discrimination testing. - **You're at the very top of the contribution range and don't care about Roth.** Both vehicles cap at $72K total contribution; if you'll always max it via employer side, SEP-IRA's simplicity wins. ## Which one fits you **Picking your vehicle: Which fits *you*?** - **You want Roth contributions** → Solo 401(k) (recommended). The employee Roth side gives tax-free withdrawals on up to **$24,500**/yr. SEP-IRA has no real Roth option. - **Moderate income, want to max what you can** → Solo 401(k) (recommended). The $24,500 employee deferral beats SEP-IRA's 25%-of-net rule for solos in the $60K-$150K range. - **You might need a loan** → Solo 401(k) (recommended). It is the only retirement vehicle that lets you borrow up to **$50K** from your own balance. SEP-IRA does not. - **Rolling in an old employer 401(k)** → Solo 401(k) (recommended). It can accept the rollover; a SEP-IRA generally cannot take a former-employer 401(k). - **You missed the Dec 31 deadline** → SEP-IRA. You can open and fund it up to your tax-filing deadline, extensions included. The Solo 401(k) plan had to exist by Dec 31. - **You have employees and want it simple** → SEP-IRA. The all-employees-proportional rule is simpler than 401(k) non-discrimination testing. - **Top of the range, no Roth need** → SEP-IRA. Both cap at $72K. If you will always max it employer-side anyway, SEP-IRA's simplicity wins. Many high-income ETS clients run both across years: Solo 401(k) for ongoing years, SEP-IRA to catch up a year that closed before Dec 31. ## The hybrid approach Many high-income ETS clients use **both**. Open a Solo 401(k) for ongoing year contributions. When a great income year happens and you're past Dec 31, fund a SEP-IRA for that year (since Solo 401(k) plan must have existed by Dec 31 of the contribution year). This double-dipping isn't possible in the same year, but across years it lets you catch up missed contributions. ## What about a Cash Balance Plan? Solo 401(k) and SEP-IRA cap at ~$72K/yr. For high-income owners ($500K+ net) approaching age 50+, a [Cash Balance plan](https://elevatedtaxstrategies.com/tax-planning/cash-balance-plan-when-it-makes-sense/) on top can shelter another $100-200K/yr. ## Common questions **Can I contribute to both a Solo 401(k) and a SEP-IRA in the same year?** Technically yes, but if you contribute to both for the same business, the contribution limits are aggregated. Most useful when one business has a Solo 401(k) and a separate business has a SEP. **What if I have employees in my business?** Solo 401(k) is only for owner + spouse. Adding non-spouse employees means upgrading to a standard 401(k) (which is doable but adds compliance cost ~$1,500-3,000/yr). SEP-IRA can include employees but requires equal-percentage contributions to all eligible employees. **Can I roll over an IRA into a Solo 401(k)?** Yes. Most brokerages let you roll over Traditional IRAs into the Solo 401(k). This is often useful for [backdoor Roth](https://elevatedtaxstrategies.com/tax-planning/backdoor-roth-ira-step-by-step/) strategy because Solo 401(k) balances don't aggregate into IRA pro-rata rules. **What if my income varies year to year?** Both plans let you skip years and vary contribution amounts. There's no minimum-funding requirement (unlike defined-benefit plans like Cash Balance). **Does my spouse working in the business have to be on payroll?** For Solo 401(k), spouse needs to be a legitimate employee (payroll + W-2 + actual work). Just being married to you isn't enough, there has to be a defensible employment relationship. --- If you're a self-employed owner and your retirement contribution capacity hasn't been modeled, the [Discovery call](https://elevatedtaxstrategies.com/discovery/) is the right next step. For high-income owners we often layer Solo 401(k) + Cash Balance + [mega-backdoor Roth](https://elevatedtaxstrategies.com/tax-planning/mega-backdoor-roth-mechanics/) + [HSA](https://elevatedtaxstrategies.com/tax-planning/hsa-as-stealth-retirement/). We'll walk you through the full retirement-stacking picture on the call.