SEP IRA vs. Solo 401(k) vs. SIMPLE IRA: Which Is Right for You? (2026)

For most self-employed business owners in 2026, the right retirement plan is a Solo 401(k) — and the entity structure that precedes that decision matters more than the plan itself. The SEP IRA works in a narrow set of cases. The SIMPLE IRA is almost never the right answer. What actually matters isn't a side-by-side limit table; it's how much net cash lands in your pocket after entity taxes, payroll taxes, and QBI interactions — and what that leaves available for retirement contributions.

"You have to take into account self-employment tax, payroll taxes, distributions, and QBI deductions. What really matters is the net cash in pocket for a given income amount, how much that allows for contribution to the retirement plan, and how that retirement plan creates a delta in the cash in pocket and balance in the retirement plan."

— Neal McSpadden, Founder, Tax Sherpa

Key Takeaways

• The standard comparison table at "$100k income" is structurally misleading — it ignores entity structure, payroll taxes, and QBI, which change every number.
• At $75k net SE income, the Solo 401(k) allows $38,440 versus $13,940 for a SEP IRA. The $24,500 gap is the employee deferral the SEP doesn't have — and it's constant at every income level.
• At $150k total S-Corp income with a $60k W-2, the Solo 401(k) allows $39,500 versus $15,000 for a SEP. Same $24,500 gap, same reason.
• The SIMPLE IRA caps total contributions at $19,250 at $75k income and carries a 25% early withdrawal penalty within the first two years.
• Retirement planning is the last step in the tax stack. Entity structure and QBI optimization come first; the retirement plan is the capstone.
• The answer to which plan wins almost always points to a 401(k) variant — Solo for owner-only businesses, safe harbor or traditional for businesses with employees.

Stop Comparing at $100k

Every SEP IRA vs. Solo 401(k) article runs the same table. Pick a round number — $100k income, sometimes $200k — show contribution limits side-by-side, conclude the Solo 401(k) wins. That framework is wrong before it starts.

Four variables the standard table ignores: entity structure (Schedule C vs. S-Corp produces entirely different contribution bases), SE and payroll taxes (reduce net income before the retirement math starts), QBI interactions (contributions reduce the §199A deduction), and distributions (S-Corp distributions don't count as compensation). An owner paying $60k W-2 on $150k total income has entirely different contribution capacity than one paying $150k W-2 on $300k total.

The honest comparison: for your specific income, entity, and payroll structure, what is net cash in pocket — and how much of that goes into a retirement account?

The 2026 Numbers, Done Correctly

2026 limits, correct formulas: SEP IRA for Schedule C filers uses approximately 20% of net SE income (not 25% — that rate applies only to W-2 wages in an S-Corp). Solo 401(k) shows employee deferral plus employer portion. SIMPLE IRA shows $17,000 employee deferral plus 3% match.

Schedule C / SMLLC

The $24,500 gap between Solo 401(k) and SEP is constant — always the employee elective deferral. At $75k net SE, the employer portion of both plans is identical ($13,940); the Solo 401(k) adds $24,500 on top.

S-Corp — W-2 + Distributions

For S-Corp owners, both the Solo 401(k) employer portion and the SEP shift to 25% of W-2 wages. W-2 salary level is the critical variable.

At $300k total with $150k W-2, the Solo 401(k) reaches $62,000 vs. $37,500 for the SEP — same $24,500 gap. Payroll taxes on the $150k W-2 run $22,950, a real cost that belongs in the comparison.

What Most Articles Get Wrong

The SEP IRA formula is not "25% of income" for Schedule C filers. The correct calculation nets out the half-SE-tax deduction first, yielding approximately 20% of gross SE income. At $75k gross SE, the 25%-myth number ($18,750) overstates the actual contribution ($13,940) by $4,810.

The SIMPLE's employer match is mandatory. The SIMPLE IRA rules require the employer to contribute either the 3% dollar-for-dollar match or the 2% non-elective. For an owner-only business, that obligation has no offsetting retention benefit.

Payroll tax on the S-Corp W-2 is a real cost. The W-2 driving employer retirement contributions also drives payroll taxes — $9,180 at $60k W-2, $22,950 at $150k W-2 — which must be netted against the contribution value.

QBI Interaction and the Tax Stack

All three plans reduce QBI. At a 20% QBI rate, a $52,381 Solo 401(k) contribution reduces the §199A deduction by approximately $10,476. The net federal tax benefit is the marginal rate on the deferral minus that offset — not the marginal rate times the full contribution amount.

Above the QBI phase-out (approximately $197,300 single / $394,600 MFJ in 2026), S-Corp W-2 wages serve as the qualifying floor. Salary strategy and retirement planning become the same decision at those levels.

This is also why retirement planning is the last step in the tax stack. Entity structure drives W-2 level; W-2 level determines contribution capacity. The retirement plan is the capstone.

The Decision Framework

Three questions resolve the answer for most clients:

Question 1: Do you have employees, and do you plan to hire them?

No employees — the Solo 401(k) is almost certainly correct. It allows the employee deferral the SEP doesn't have, supports Roth, and permits mega-backdoor Roth through select custodians. It closes permanently once a non-spouse W-2 employee joins the business. Yes, or hiring likely within two years — see the Retirement Plans With Employees page in this hub for the employer plan framework.

Question 2: What matching structure fits?

The SEP IRA is occasionally viable for very small employers, but its "playing fair" requirement — any owner contribution rate applies proportionally to all eligible employees — limits its usefulness quickly. The SIMPLE IRA almost never wins: mandatory match, $17,000 ceiling, and 25%-within-two-years withdrawal penalty make it a plan to migrate away from.

Question 3: Should new employees be auto-enrolled by default?

SECURE 2.0 requires auto-enrollment for 401(k) plans established after December 29, 2022 — default deferral 3%–10%, auto-escalating annually. Exemptions for businesses under 10 employees and those under three years old. Default inclusion is the safer design; opt-out rates are low in practice, which translates to real participation and a real employer cost to model.

The answer almost always points to a 401(k). Solo for owner-only businesses. Safe harbor or traditional for businesses with employees.

When the SEP IRA Still Makes Sense

Three narrow cases:

• States penalizing S-Corp election. Tennessee and DC impose taxes on S-Corp income that can eliminate payroll tax savings. In those states, Schedule C may remain more efficient, and the SEP's October 15 filing-extension deadline makes it useful for retroactive contributions.
• Missed the December 31 Solo 401(k) setup deadline. The Solo 401(k) requires a December 31 establishment date. The SEP can be opened and funded through the extended return deadline.
• Simplicity as the overriding priority. No Form 5500-EZ, no discrimination testing. For an owner who won't maintain a more complex plan, the SEP's reduced friction has value.

Outside these cases, the Solo 401(k) outperforms the SEP above roughly $24,500 in net SE income. When the $72,000 combined limit isn't enough, the next step is a cash balance plan stacked on top — not a different IRA.

FAQ

Why do comparison articles show the Solo 401(k) and SEP IRA having the same maximum?

Both plans cap at $72,000 — the IRC §415 defined contribution limit. The SEP reaches it through employer contributions alone. The Solo 401(k) reaches it via employee deferral plus employer contribution. They look equal at the maximum but diverge significantly below $100k, where the deferral gap is the entire difference.

Can I contribute to both a SEP IRA and a Solo 401(k) in the same year?

Technically yes, practically no. The $72,000 global limit doesn't change — having both plans allocates the same room across two structures. The narrow case: a Schedule C-to-S-Corp conversion mid-year creates income in both structures, supporting contributions to each for its respective period. That's a transition-year edge case, not a planning strategy.

I've been using a SEP IRA for five years. Should I switch?

If you have no employees and can establish a Solo 401(k) by December 31, the math almost always favors switching. An extra $24,500 per year compounds substantially over a decade. The right first step is a Summit Strategy Session to model entity structure, salary, QBI, and retirement together before changing anything.

Does the QBI phase-out affect which plan to choose?

Yes. Above the phase-out threshold, S-Corp W-2 wages serve as the qualifying floor for the QBI deduction. The employer retirement contribution must be sized alongside the W-2 to preserve the full deduction. Salary strategy and retirement planning become the same decision.

Need Help Comparing Retirement Plans?

Tax Sherpa helps solopreneurs and small business owners pick the retirement plan that fits your entity, income, and employee situation — not a generic comparison chart.

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