SEP-IRA vs Solo 401(k) for single-owner S-Corp retail business

Updated: July 28, 2026

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The retirement-plan question for a single-owner S-corp retail business is usually framed as a coin flip between simplicity and capacity. SEP-IRA wins on simplicity; Solo 401(k) wins on capacity. That framing almost never produces the right answer at the modest-W-2 profile that fits most second-career retail S-corps.

A 56-year-old retired police lieutenant runs a small single-owner S-corp on the side. He draws $60,000 of W-2 wages and leaves the rest as a Schedule K-1 distribution. At that income level, the Solo 401(k) delivers a tax-deferred contribution ceiling roughly four times higher than the SEP-IRA.

our OPRS 2026 gold IRA vetting report before any custodian decision. A self-directed SEP or Solo 401(k) holding IRS-approved bullion under IRC Section 408(m)(3) is constrained by the dealer chain on the other end of the custodian relationship.

Element I is the SEP-IRA structure under IRC Section 408(k): employer-only contributions, uniform percentage across eligible employees, simple administration. Element II is the Solo 401(k) structure under IRC Section 401(k): two-piece contributions, age-50 catch-up under Section 414(v), Roth option, Form 5500-EZ filing at $250,000 assets. Element III is the W-2-wage math that flips the verdict between the two plans.

Element IV is the verdict per single-owner S-corp retail profile, including the second-career public safety officer running a side business with $200,000 to $400,000 still parked in a governmental 457(b).

What a SEP-IRA actually gives a single-owner S-corp

A Simplified Employee Pension IRA, or SEP-IRA, is an employer-funded retirement account established under IRC Section 408(k). The S-corp acts as the employer and the single owner is the only eligible employee.

Contributions come exclusively from the corporation, sized at up to 25 percent of W-2 wages, with a 2025 annual ceiling of $70,000 under IRC Section 415(c) annual additions limit.

The 25 percent applies to W-2 Box 1 wages plus any pretax salary deferrals, not to S-corp Schedule K-1 distributions. The distribution side of S-corp compensation is not eligible compensation for any qualified retirement plan under IRC Section 415(c)(3) and the IRS plan participant compensation guidance.

There is no employee deferral side and no age-50 catch-up under a SEP-IRA. Contributions are discretionary year by year, and the contribution deadline is the tax filing deadline plus extensions, which gives most S-corp owners until October 15 of the following year to fund the prior tax year.

Administration is among the lightest of any qualified plan. There is no Form 5500 filing for a single-owner SEP, no annual nondiscrimination testing, and no plan document drafting beyond a one-page IRS Form 5305-SEP or a prototype from the custodian. IRS SEP Plan Sponsor guidance covers the establishment mechanics.

The structural ceiling that flips the verdict against the SEP-IRA at modest income shows up in the eligible-employee rule.

If the S-corp later hires any non-spouse W-2 employee who meets the SEP-IRA eligibility threshold, the owner must contribute the same percentage of W-2 wages to that employee as to themselves. The threshold is typically three of the last five years of service with at least $750 in compensation as of 2025 under IRC Section 408(k)(2).

A 25 percent owner allocation forces a 25 percent employee allocation, which most single-owner S-corp retail businesses cannot absorb. The eligibility window is wide and historical: an employee who worked three out of the prior five years counts even after a hiatus.

What a Solo 401(k) actually gives a single-owner S-corp

A Solo 401(k), also called an Individual 401(k) or one-participant 401(k), is a standard qualified retirement plan under IRC Section 401(k). It is restricted to businesses with no W-2 employees other than the owner and the owner’s spouse. Its two-piece contribution structure is what separates it from the SEP-IRA.

The employee elective deferral side accepts up to $23,500 in 2025 under IRC Section 402(g), plus an age-50 catch-up of $7,500 under IRC Section 414(v), for a $31,000 employee piece.

The employer profit-sharing side accepts the same 25 percent of W-2 wages as the SEP-IRA. The combined employee plus employer total is capped at the same $70,000 annual additions limit under IRC Section 415(c). With the age-50 catch-up, that ceiling rises to $77,500.

The Solo 401(k) also unlocks features the SEP-IRA does not offer. Those include a Roth deferral option on the $23,500 employee piece and a plan-loan option of up to $50,000 or 50 percent of the account balance under IRC Section 72(p). The SECURE Act 2.0 age 60 to 63 super catch-up raises the limit to $11,250 in 2025 in place of the standard $7,500. A Roth employer match option became available after SECURE Act 2.0 where the custodian supports it.

The trade-off is administrative weight. A Solo 401(k) requires a plan document (custodian prototype is usually fine), and once plan assets cross $250,000, the owner must file Form 5500-EZ annually with the IRS. The plan-establishment deadline is December 31 of the contribution year for the employee deferral piece, with employer profit sharing fundable through the tax-filing extension deadline.

The eligibility constraint is sharper than the SEP-IRA’s. A Solo 401(k) becomes structurally ineligible the moment a non-spouse W-2 employee works more than 500 hours in a year under the SECURE Act 2.0 long-term part-time employee rule, codified at IRC Section 401(k)(2)(D).

A retail business that hires even a part-time clerk for 11 hours a week crosses that threshold within a year. The fallback at that point is to convert to a traditional 401(k) with nondiscrimination testing or to terminate the Solo 401(k) and roll to a SEP-IRA or IRA.

Side-by-side specs: SEP-IRA vs Solo 401(k) at the single-owner S-corp profile

The table below compares the structural specs at the single-owner S-corp retail business profile with no current non-spouse W-2 employees. The Status column flags the typical winner for the profile.

The contribution math: what each plan accepts at three W-2 wage levels

The dollar throughput at modest W-2 wages is the single biggest reason a single-owner S-corp retail business chooses Solo 401(k) over SEP-IRA. The chart below shows the maximum tax-deferred contribution the plan accepts at three illustrative W-2 wage levels for an owner aged 50 plus, using 2025 limits. The SEP-IRA bar is the 25 percent employer share alone.

The Solo 401(k) bar is the $23,500 employee deferral plus the 25 percent employer share, plus the $7,500 age-50 catch-up under IRC Section 414(v).

At $40,000 of W-2 wages, the SEP-IRA accepts $10,000 (25 percent of $40,000) while the Solo 401(k) accepts $41,000 (the $23,500 employee deferral plus the $10,000 employer share plus the $7,500 catch-up). At $80,000 of W-2 wages, the gap narrows in percentage terms but widens in absolute dollars: $20,000 for the SEP vs $51,000 for the Solo.

At $150,000 of W-2 wages, the SEP catches up at $37,500 vs the Solo’s $68,500.

The two plans converge at the 2025 $77,500 cap (with catch-up) when W-2 wages cross approximately $187,000; beyond that point, the SEP-IRA’s simpler administration becomes the operative consideration. Check the custodian against the 2026 OPRS list if any portion of the funded balance is destined for a self-directed bullion allocation.

The five-step decision sequence for a single-owner S-corp retail business

The decision sequence below is the procedural framework most single-owner S-corp owners can run before bringing in a tax-and-retirement advisor for the final allocation review. Step 4 is where independent counsel adds the most value at the modest-revenue retail profile.

Step 1. Confirm S-corp election is active and W-2 wages are set. The retirement plan choice runs off W-2 wages, not gross corporate revenue or net S-corp profit.

If the owner has not yet drawn W-2 wages in the current tax year, the planning window closes fast. W-2 wages must appear on a quarterly Form 941 and a year-end W-2 to count as compensation under IRC Section 415(c)(3). A pure Schedule K-1 distribution year disqualifies the year for both plans.

Step 2. Estimate W-2 wages for the contribution year. The estimate determines the contribution headroom on each plan side and the deferral-vs-profit-share allocation on the Solo 401(k) side. At modest wages under $80,000, the employee deferral side of the Solo carries most of the contribution. At wages above $200,000, the SEP-IRA’s simpler administration becomes the operative consideration.

Step 3. Decide tax-deferred vs Roth allocation. If the owner expects to be in a higher tax bracket in retirement, the Solo 401(k) Roth deferral side adds material long-term value. A separated public safety officer with pension and Social Security stacking is the canonical case. The SEP-IRA’s Roth option under SECURE 2.0 is statutorily available but operationally rare at most custodians as of 2025. The Solo 401(k) Roth has been broadly supported for over a decade.

Step 4. Evaluate hiring plans over the next 3 to 5 years. A non-spouse W-2 hire at 500 hours per year terminates the Solo 401(k) eligibility under SECURE 2.0. The SEP-IRA forces uniform percentage contributions across eligible employees once they meet the three-of-last-five-years threshold. A retail business with seasonal staff or a hiring trajectory should weigh the SEP-IRA’s flexibility against the Solo 401(k)’s capacity. This is the step where most single-owner S-corps benefit from outside counsel.

Step 5. Open the plan before year-end and fund through the extension deadline. The Solo 401(k) plan document must be in place by December 31 of the contribution year for the employee deferral piece (SECURE Act 2.0 modestly relaxed the deadline for employer-only Solo contributions).

The SEP-IRA can be opened and funded up to the tax-filing deadline plus extensions, typically October 15 of the following year. For a separated public safety officer also weighing a partial 457(b) rollover into the side-business plan, the rollover timing layers on top of the contribution timing and benefits from advisor coordination.

Verdict per single-owner S-corp profile

Profile A: separated public safety officer age 50 to 58, single-owner S-corp retail business with W-2 wages of $40,000 to $100,000, no current non-spouse W-2 employees, no hiring plans over the next 3 years. The Solo 401(k) wins.

The $23,500 employee deferral plus the $7,500 age-50 catch-up under IRC Section 414(v) delivers between $33,500 and $48,500 of contribution capacity that the SEP-IRA cannot reach at this wage level. The Roth deferral option also fits the second-career profile where pension and Social Security income raise the retirement-year marginal bracket.

A partial rollover from a governmental 457(b) into the Solo 401(k) is allowed. The PSO 72(t)(2)(A)(v) age-50 exception under IRC Section 72(t)(10) remains available on the rolled balance, provided separation occurred at age 50 or later.

Profile B: single-owner S-corp with W-2 wages of $280,000 plus, no hiring plans, strong administrative-simplicity preference. The SEP-IRA wins. At $280,000 W-2 wages, the 25 percent employer share alone delivers $70,000, hitting the IRC Section 415(c) cap with zero Form 5500-EZ filing obligation, no plan document maintenance, and no employee-deferral payroll wiring. The Solo 401(k)’s catch-up adds only $7,500 of incremental capacity, which most owners at this profile do not value enough to justify the $250,000-assets Form 5500-EZ trigger.

Profile C: single-owner S-corp planning to hire 1 to 2 W-2 employees within 3 years. Neither plan is ideal. The Solo 401(k) terminates eligibility the moment a non-spouse employee crosses the SECURE 2.0 long-term part-time threshold. The SEP-IRA’s uniform-percentage rule turns a 25 percent owner allocation into a 25 percent employee allocation, which most retail margins cannot absorb.

The SIMPLE IRA under IRC Section 408(p) becomes the operative comparison at that point; SEP-IRA wins on owner-side contribution capacity but at the cost of mandatory employee contributions.

Profile D: single-owner S-corp owner age 50 plus considering a partial rollover from a governmental 457(b) or other qualified plan into the side-business retirement plan. Either plan accepts the incoming rollover under IRC Sections 408(d)(3) and 401(a)(31). The Solo 401(k) preserves more downstream optionality: in-service distribution rules, the loan feature, and the Roth conversion-within-plan path under IRC Section 402A(c)(4). The dealer choice on the gold IRA leg of the rolled balance still precedes the plan choice.

When neither SEP-IRA nor Solo 401(k) fits

Neither plan fits when the S-corp has multiple non-spouse W-2 employees who already cross the eligibility thresholds. Neither fits when the owner’s W-2 wages are too low to support meaningful contributions, meaning under $20,000 for the year. And neither fits when the owner needs creditor protection exceeding the federal IRA-bankruptcy cap.

A multi-employee retail S-corp moves the comparison to a SIMPLE IRA under IRC Section 408(p), a traditional 401(k) with safe-harbor election under IRC Section 401(k)(12), or a defined-benefit plan for high-income late-stage savers.

A separated public safety officer who can ladder pension and 457(b) income to bridge to age 59 and a half may not need the side-business contribution at all in the early years. The dealer screen applies to any gold IRA position inside the broader retirement plan, whether the retirement plan is SEP, Solo 401(k), or another structure.

Where Augusta sits in the dealer landscape for this scenario

Augusta Precious Metals sits on the OPRS three-dealer shortlist.

OPRS verifies four trust-signal markers on a public-only basis for any dealer in the precious metals IRA cluster. The first two are Money Magazine Best Overall Gold IRA Company (2022 to 2026) and Investopedia Most Transparent Gold IRA Company (2022 to 2026). The last two are BBB A+ Rating with Zero Complaints (accredited since 2014) and 4,000-plus 5-star ratings aggregated across Trustpilot, Google, and Consumer Affairs.

The dealer minimum is industry-reported around $50,000, which fits a typical Profile A owner who pairs an annual Solo 401(k) contribution with a partial governmental 457(b) rollover into the same self-directed plan.

Augusta’s Learn-Talk-Decide process is guided by salaried, non-commissioned educators and works well for planning conversations that include the spouse and, where applicable, a fiduciary advisor, particularly when the goal is keeping the account clean for a surviving spouse or heirs.

Can a single-owner S-corp run both a SEP-IRA and a Solo 401(k) in the same tax year?

Yes in principle, no in practice for most owners. The IRC Section 415(c) annual additions cap applies on a combined basis across both plans when both are maintained by the same employer; the $70,000 total contribution ceiling does not multiply.

The combined-plan path is occasionally used to capture a SEP-IRA contribution funded after the Solo 401(k) deferral deadline has passed, but the SECURE Act 2.0 deadline relaxation made the dual-plan pattern less useful. A standard single-owner S-corp picks one plan per year. The IRS one-participant 401(k) plans guidance covers the combined-cap mechanics.

Does a Solo 401(k) lose its eligibility the moment the S-corp hires a non-spouse part-time employee?

The Solo 401(k) tips into ineligibility under SECURE Act 2.0 once a non-spouse W-2 employee works at least 500 hours in two consecutive years (under the long-term part-time employee rule effective 2024). A single year above 500 hours does not immediately disqualify the plan, but planning becomes urgent.

At the disqualification point, the plan must convert to a traditional 401(k) with nondiscrimination testing or terminate and roll to a SEP-IRA or IRA. Watching the hours threshold across part-time hires is part of the annual plan compliance review for any single-owner S-corp retail business.

Can the Solo 401(k) hold IRS-approved gold bullion the same way a self-directed IRA can?

Yes, a self-directed Solo 401(k) can hold IRS-approved bullion under IRC Section 408(m)(3) when the plan document permits and the custodian supports physical-metal custody. The same purity floors apply: 99.5 percent for gold (American Gold Eagle is the named statutory exception under IRC Section 408(m)(3)(A)), 99.9 percent for silver, 99.95 percent for platinum and palladium.

The Solo 401(k) trustee, the depository, and the dealer infrastructure all need to align; thin operations on any of the three legs surface at distribution time. The OPRS dealer shortlist names the three operators with the publicly verifiable trust-signal stack for the side-business owner who wants a bullion allocation inside the side-business retirement plan.

Does a partial 457(b) rollover into a Solo 401(k) preserve the public safety officer age-50 exception?

The PSO 72(t)(2)(A)(v) age-50 exception under IRC Section 72(t)(10) applies to distributions from a qualified retirement plan after separation in the year of age 50 or later.

A governmental 457(b) rolled into a Solo 401(k) maintained by the side-business S-corp preserves the exception on the rolled balance. The Solo 401(k) trustee must be able to document the public safety officer status and the separation date at the time of any pre-59-and-a-half distribution. The exception does not require the receiving plan to be the original employer’s plan.

The operational risk is on the documentation side: a Form 1099-R coded as an early distribution can be corrected on Form 5329 but the friction is real. IRC Section 72(t)(10) at Cornell Legal Information Institute is the governing statute.

Sources cited

1. IRC Section 408, Individual Retirement Accounts, and Section 408(k) Simplified Employee Pensions
2. IRC Section 401, Qualified Pension, Profit-Sharing, and Stock Bonus Plans
3. IRC Section 414(v), Catch-Up Contributions for Individuals Age 50 or Over
4. IRC Section 415(c), Limitation for Defined Contribution Plans
5. IRC Section 402(g), Limitation on Exclusion for Elective Deferrals
6. IRC Section 408(m)(3), Bullion Permitted in IRAs
7. IRC Section 72(t)(10), Public Safety Officers Age-50 Exception
8. IRS Simplified Employee Pension Plan Sponsor Guidance
9. IRS One-Participant 401(k) Plans Sponsor Guidance
10. IRS Form 5500 Corner, including Form 5500-EZ for One-Participant Plans
11. IRS Retirement Topics, Definition of Compensation for Qualified Plans
12. IRS In-Plan Rollovers from Tax-Deferred 401(k) Accounts to Roth 401(k) Accounts

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