How Much Can an S-Corp Owner Put in a Solo 401(k)? (w/Examples) + FAQs

This article reflects federal rules as of June 2026 and covers tax years 2025 and 2026. It also notes state-conformity issues at a general level. Tax law changes often — confirm current figures with the IRS or a licensed tax professional before you file. This guide is educational and is not a substitute for personal advice from a CPA or tax attorney for your specific situation.

Quick Answer

Up to $70,000 for tax year 2025 and up to $72,000 for tax year 2026 if you are under age 50. The total is split between an employee deferral and an employer contribution capped at 25% of your W-2 wages. Catch-ups push the 2026 ceiling to $80,000 (age 50+) or $83,250 (age 60–63).

As an S-corp owner, you wear two hats in your own Solo 401(k): you are the employee and the employer. That dual role is the whole reason the plan is so powerful, but it also creates a trap that catches many owners — your employer contribution is locked to 25% of the W-2 salary your S-corp pays you, not to your total profit. Set your salary too low to dodge payroll tax and you quietly shrink how much you can stuff into retirement.

The stakes are real and time-sensitive. Your employee deferral generally has to be elected and run through payroll by December 31, while the employer piece can wait until your business tax-filing deadline. According to the Investment Company Institute’s retirement data, 401(k) plans held more than $8.7 trillion in assets — and Solo 401(k)s let one-owner businesses tap those same rules at the highest contribution ceilings available to the self-employed, per IRS one-participant 401(k) guidance.

Here is what you will walk away knowing:

💵 The exact 2025 and 2026 dollar limits, broken into the employee and employer pieces, with the catch-ups for ages 50+ and 60–63.
🧮 Fully worked examples showing how a real S-corp salary turns into a real contribution — copy the math.
⚖️ The “reasonable salary” tension: how a lower salary saves payroll tax but cuts your retirement contribution, and how to balance both.
🏦 How to add Roth and the mega backdoor Roth, plus how putting a spouse on payroll can nearly double the household total.
🗓️ The deadlines, the seven costly mistakes, and the next steps to set up and fund your plan correctly.

How a Solo 401(k) Works for an S-Corp Owner

A Solo 401(k) — also called a one-participant 401(k) or individual 401(k) — is a retirement plan for a business with no full-time employees other than the owner and a spouse, as defined in IRS one-participant 401(k) rules. It is not a different kind of 401(k); it is a regular 401(k) that the IRS lets a solo business run with far less paperwork. The moment you hire a non-spouse employee who works enough hours, the “solo” status ends.

For an S-corporation owner, the key fact is that you receive W-2 wages from your own corporation. That W-2 number is the engine for every contribution calculation in the plan. Your S-corp profit that flows through on Schedule K-1 does not count as compensation for plan purposes — only the wages reported in Box 1 / Box 5 of your W-2 do. This single rule separates S-corp owners from sole proprietors and is the source of most confusion.

You contribute in two roles. As the employee, you make an elective deferral out of your paycheck. As the employer, your S-corp makes a profit-sharing contribution on your behalf. Both land in the same account, and both count toward one combined annual limit set under Internal Revenue Code Section 415(c). Understanding which dollars come from which hat is the whole game, because each hat has its own cap and its own deadline.

The two hats: employee vs. employer

Wearing both hats means two separate buckets of money with two separate rules. The employee deferral is a flat dollar limit you can hit regardless of how high your salary is, as long as your salary is at least that amount. The employer contribution is a percentage of salary, so it grows only as your W-2 wages grow.

The consequence of confusing the two is costly: many owners assume their profit drives the employer contribution, then over-contribute and trigger a correction. The fix is to remember the employer side is always 25% of W-2 wages for an S-corp, full stop, as explained in IRS retirement plan FAQs.

A common misconception is that an S-corp owner can base contributions on distributions or total business income. You cannot, and doing so inflates your contribution beyond the legal cap. What you should do: pull your final W-2 wage figure before you calculate anything, and run the employer math on that number alone.

The 2025 and 2026 Contribution Limits, Decoded

The total Solo 401(k) limit is one number made of two parts. For tax year 2025 the combined ceiling is $70,000 before catch-ups, and for tax year 2026 it rises to $72,000, per IRA Financial’s 2026 limit breakdown. Catch-up contributions sit on top of those totals for older owners.

The employee deferral limit is $23,500 for 2025 and $24,500 for 2026, confirmed by ADP’s 401(k) limit table. On top of that, the standard catch-up for ages 50 and over is $7,500 in 2025 and $8,000 in 2026. A SECURE 2.0 “super catch-up” for ages 60–63 is $11,250 and replaces (does not stack with) the standard catch-up, as detailed by CNBC on super catch-up rules.

The employer profit-sharing contribution is capped at 25% of your W-2 wages for an S-corp, and the dollar value of that 25% slice can reach $46,500 in 2025 and $47,500 in 2026, per IRA Financial’s contribution guide. The employee and employer pieces together cannot exceed the combined 415(c) ceiling, plus any catch-up you qualify for.

Contribution piece	Tax year 2025	Tax year 2026
Employee deferral (under 50)	$23,500 (ADP)	$24,500 (IRA Financial)
Age 50+ catch-up	+$7,500	+$8,000
Age 60–63 super catch-up (instead of 50+)	+$11,250	+$11,250
Employer (max 25% of W-2 wages)	up to $46,500	up to $47,500
Combined max, under 50	$70,000	$72,000
Combined max, age 50–59 or 64+	$77,500	$80,000
Combined max, age 60–63	$81,250	$83,250

Why the 25% cap matters so much for S-corps

The 25% rule is the single biggest difference between an S-corp owner and a sole proprietor. A sole proprietor uses roughly 20% of net self-employment income, while an S-corp owner uses 25% of W-2 wages, per IRA Financial’s plan rules. The percentages look different only because the sole-proprietor figure is adjusted for self-employment tax.

The consequence is direct: your employer contribution is hostage to your salary. If your S-corp pays you $80,000, the most the company can put in as profit sharing is $20,000 (25% of $80,000), no matter how large your profit is. Set the salary low and the employer bucket shrinks with it.

A frequent misconception is that an S-corp owner can “make up” a small salary with a bigger employer contribution. You cannot — the 25% cap is hard. What you should do: if maxing the plan matters more than shaving payroll tax, model your salary against the contribution you want before you run year-end payroll.

Worked Examples: Turning Salary Into a Contribution

Here is the math you can copy. The employee deferral is a flat amount; the employer piece is 25% of your W-2 wages; the two added together cannot pass the annual ceiling.

Example 1 — Maria, age 45, $120,000 W-2 salary (tax year 2026). Maria defers the full employee max of $24,500. Her S-corp adds 25% of $120,000 = $30,000 as the employer contribution. Total: $24,500 + $30,000 = $54,500. She is under the $72,000 ceiling, so every dollar counts and nothing is wasted.

Example 2 — David, age 52, $200,000 W-2 salary (tax year 2026). David defers $24,500 plus the $8,000 age-50 catch-up = $32,500. The employer 25% of $200,000 would be $50,000, but the employer piece is capped so the non-catch-up total stays at $72,000. So employer = $72,000 − $24,500 = $47,500. Add the catch-up: $47,500 + $24,500 + $8,000 = $80,000, the exact age-50+ maximum for 2026.

Example 3 — Priya, age 61, $190,000 W-2 salary (tax year 2026). Priya qualifies for the $11,250 super catch-up. Her employer 25% of $190,000 = $47,500 (the cap). She defers $24,500, then adds the $11,250 super catch-up. Total: $47,500 + $24,500 + $11,250 = $83,250, the top 2026 figure for ages 60–63.

The “magic number” salary to max out

If your only goal is to max the plan with the lowest possible salary, there is a target wage. To fully fund both buckets in pre-tax form, an S-corp owner needs roughly $186,000 in W-2 wages regardless of age, because $186,000 × 25% ≈ $46,500 employer plus the employee deferral, per My Solo 401k’s S-corp magic number guide.

If you only want to max the employee deferral, you need W-2 wages of at least $23,500 (2025) or $24,500 (2026). The consequence of a salary below that is simple — you cannot defer more than you earn in wages.

A common misconception is that any salary unlocks the full $70,000–$72,000. It does not; the employer 25% only reaches $46,500–$47,500 at about $186,000–$190,000 of wages. What you should do: pick the salary that matches your real goal — minimum deferral, balanced, or full max — and confirm it is still a reasonable wage.

Which Situation Applies to You?

The right answer depends on what you are trying to do right now. Use this to jump to the path that fits.

You want the highest possible contribution: aim for about $186,000–$190,000 in W-2 wages so the 25% employer piece tops out — see the worked examples above.
You want to minimize payroll tax: keep your salary at the lowest reasonable level, accept a smaller employer contribution, and lean on the employee deferral.
You are age 50–63: add the catch-up ($8,000 for 2026) or the super catch-up ($11,250 for ages 60–63) on top of the standard ceiling.
You want tax-free growth: use Roth deferrals and consider the mega backdoor Roth (covered below).
You have a working spouse: put them on payroll to roughly double the household contribution (covered below).

The Reasonable Salary Tension

Every S-corp owner faces the same tug-of-war. A lower W-2 salary cuts the 15.3% Social Security and Medicare tax you pay, but it also shrinks the 25% employer contribution and your maximum employee deferral. The IRS requires S-corp owners to pay themselves a reasonable salary for the work they do, as covered in IRS S-corporation compensation guidance.

The consequence of going too low is twofold. First, the IRS can reclassify your distributions as wages, hitting you with back payroll taxes, penalties, and interest. Second, a tiny salary mechanically caps your retirement contribution — a $40,000 salary limits the employer piece to $10,000, no matter how profitable the business is.

A widespread misconception is that “reasonable” means as low as you can argue. It means what a comparable worker would earn for the same role, based on facts like duties, time, and industry pay. What you should do: document how you set your salary, and if you want to max the Solo 401(k), price the higher salary’s payroll-tax cost against the bigger retirement contribution and the deduction it creates.

Salary strategy for tax year 2026	What happens to your contribution
Low salary ($50,000) to cut payroll tax	Employer piece capped at $12,500 (25%); total with deferral about $37,000; payroll tax lower but contribution smaller
High salary (~$190,000) to max the plan	Employer piece reaches the $47,500 cap; full $72,000 (under 50) available; payroll tax higher but bigger deduction

Roth and the Mega Backdoor Roth

Your employee deferral can be made pre-tax or Roth — Roth contributions are after-tax now but grow tax-free, with qualified withdrawals tax-free in retirement, per IRS Roth account rules. For ages 50+, note that SECURE 2.0 requires catch-up contributions to be Roth for higher earners (wages above $145,000, indexed), so plan for that wrinkle.

The mega backdoor Roth is the advanced move. If your plan document allows voluntary after-tax contributions and in-plan Roth conversions, you can contribute after-tax dollars up to the overall 415(c) limit and convert them to Roth, as described by My Solo 401k on after-tax contributions. This lets a high earner route the full $70,000–$72,000 into Roth treatment instead of pre-tax.

The consequence of skipping the right plan document is that you simply cannot do this — most free brokerage Solo 401(k) plans (Fidelity, Schwab) do not allow after-tax contributions or in-plan conversions. A common misconception is that any Solo 401(k) supports the mega backdoor Roth. What you should do: if Roth maxing is your goal, open a plan with a provider whose document explicitly permits voluntary after-tax contributions and in-plan Roth rollovers.

Adding a Spouse to Nearly Double the Total

If your spouse genuinely works in the S-corp and receives W-2 wages, they can join the same Solo 401(k) as a second participant, per IRS one-participant 401(k) rules. Each spouse gets their own full set of limits — their own deferral and their own 25% employer contribution based on their own wages.

For tax year 2026, two under-50 spouses could contribute up to $144,000 combined, and two 50+ spouses up to $160,000, per IRA Financial’s couples figures. The spouse’s wages must be real and reasonable for the work performed — paper-only salaries do not hold up.

Example 4 — The Nguyen household, both age 48 (tax year 2026). Lan earns $150,000 in W-2 wages and David earns $100,000. Lan contributes $24,500 + $37,500 (25%) = $62,000; David contributes $24,500 + $25,000 = $49,500. Together: $111,500 in one year. The consequence of skipping this when a spouse already helps run the business is leaving tens of thousands of tax-advantaged dollars on the table. What you should do: put the spouse on payroll at a defensible wage and document their duties.

Deadlines, Costs, and Timing

Timing decides whether your contribution counts for the year. The two hats have two different clocks, and missing the employee-side clock is the most common and least forgivable error.

The employee deferral must generally be elected by December 31 of the tax year and run through your S-corp payroll, because it comes out of your W-2 wages, per IRA Financial’s deadline table. The employer contribution can be made up to your business tax-filing deadline, including extensions — for an S-corp, March 15, or September 15 with an extension. The plan itself must be established by the deadlines set under SECURE 2.0 to count for the prior year.

Costs are modest. Free Solo 401(k) plans exist at Fidelity and Schwab, while document providers that allow checkbook control, loans, and the mega backdoor Roth typically charge a setup fee plus an annual fee. The consequence of choosing the cheap plan is fewer features; the consequence of missing the year-end deferral election is losing that contribution year entirely. What you should do: open the plan and set your deferral election well before December.

Mistakes to Avoid

Basing the employer contribution on profit, not W-2 wages. This over-contributes and forces a corrective distribution, which can be taxable and penalized.
Setting an unreasonably low salary. It caps your contribution and invites an IRS reclassification with back payroll taxes and penalties.
Missing the December 31 deferral election. The employee deferral must run through payroll for the year; miss it and that bucket is gone.
Counting distributions as compensation. S-corp distributions are not eligible pay; including them inflates your limit illegally.
Hiring a non-spouse employee and keeping the “solo” plan. A full-time employee usually ends solo eligibility and triggers costly compliance rules.
Forgetting Form 5500-EZ when assets exceed $250,000. Skipping it can trigger steep IRS late-filing penalties, per IRS Form 5500-EZ guidance.
Assuming any plan allows the mega backdoor Roth. Most free plans do not; contributing after-tax without the right document creates an excess contribution.
Double-counting the employee deferral across two jobs. Your deferral limit is shared across all 401(k) plans you participate in, even at a day job.

Do’s and Don’ts

Do’s

Do pull your final W-2 wage number before calculating anything, because every limit keys off it.
Do pay a reasonable salary that you can document, to protect both your taxes and your contribution room.
Do elect your employee deferral and run it through payroll before December 31, since that clock is strict.
Do add a working spouse to the plan when it fits, because it can nearly double the household total.
Do file Form 5500-EZ once plan assets cross $250,000, to avoid large penalties.

Don’ts

Don’t base the employer piece on profit or distributions, because only W-2 wages count.
Don’t assume a low salary unlocks the full limit, since the 25% cap scales with wages.
Don’t contribute after-tax dollars in a plan that doesn’t allow it, as that creates an excess contribution.
Don’t ignore the Roth catch-up rule for high earners, because it changes how your catch-up must be made.
Don’t skip professional advice on salary, since the reasonable-compensation line is where audits start.

Pros and Cons

Pros

High limits. Up to $72,000 in 2026 (plus catch-ups) — the most available to a one-owner business.
Two contribution sources. The employee + employer structure lets you save more at a given income than a SEP-IRA.
Roth flexibility. You can choose Roth deferrals and, with the right plan, the mega backdoor Roth.
Loan access. Many plans allow a loan of up to 50% of the balance, capped at $50,000.
Spouse inclusion. A working spouse roughly doubles the household ceiling.

Cons

Tied to W-2 wages. A low S-corp salary mechanically limits the employer contribution.
Payroll required. Deferrals must run through payroll, adding administrative steps.
Solo-only. Hiring full-time staff usually ends eligibility.
Form 5500-EZ filing. Required once assets pass $250,000, with penalties for late filing.
Plan limits vary. Free plans often lack loans, after-tax contributions, and Roth conversions.

State Conformity Note

Federal law sets the contribution limits, but states decide how they tax the contributions and withdrawals. Most states with an income tax follow the federal treatment of pre-tax 401(k) deferrals, meaning the deferral reduces state taxable income too. The federal employer contribution is a business deduction at the S-corp level and generally flows through consistently for state purposes.

The consequence of assuming uniformity is a surprise state bill, especially in states that diverge on Roth or retirement income. A few states — such as Pennsylvania — treat some retirement contributions and distributions differently from the federal rule. What you should do: confirm your specific state’s treatment with your state’s department of revenue or a local CPA, since conformity genuinely varies and a wrong assumption can cost you at filing.

What to Do Next

Confirm your W-2 wages for the year — this number drives every calculation.
Pick your goal: minimum deferral, balanced, or full max, and set a reasonable salary that supports it.
Open the plan with a provider whose document matches your needs (Roth, loans, mega backdoor Roth) before year-end.
Elect your employee deferral and run it through payroll by December 31.
Make the employer contribution by your S-corp filing deadline — March 15, 2027, for tax year 2026, or September 15 with an extension.
Gather records: W-2, payroll reports, plan documents, and contribution confirmations.
Call a CPA if your salary, multi-job deferrals, or mega backdoor Roth setup are complex — this is where mistakes get expensive.

FAQs

How much can an S-corp owner contribute to a Solo 401(k) in 2026? Up to $72,000 under age 50, $80,000 at age 50–59, or $83,250 at ages 60–63. That is the employee deferral plus an employer contribution capped at 25% of your W-2 wages, per IRA Financial.

What is the employer contribution limit for an S-corp owner? 25% of your W-2 wages, reaching a dollar cap of $46,500 for 2025 and $47,500 for 2026. It is based on wages only, never on profit or distributions, per IRA Financial.

Can an S-corp owner use distributions to calculate contributions? No. Only W-2 wages count as eligible compensation. Distributions and Schedule K-1 profit do not qualify, which is why your salary level controls your maximum employer contribution.

What salary do I need to max out a Solo 401(k) as an S-corp owner? About $186,000–$190,000 in W-2 wages for tax year 2026, so the 25% employer piece reaches its cap, per My Solo 401k.

Can I make Roth contributions in a Solo 401(k)? Yes. Employee deferrals can be Roth, and some plans allow a mega backdoor Roth using voluntary after-tax contributions, per My Solo 401k.

Can my spouse also contribute to our Solo 401(k)? Yes, if the spouse earns W-2 wages from the S-corp. Each spouse gets full limits, raising the 2026 couple total to about $144,000 (under 50), per IRA Financial.

When is the deadline to contribute? December 31 to elect the employee deferral through payroll, and your business filing deadline (March 15, or September 15 with an extension) for the employer contribution, per IRA Financial.

What is the super catch-up contribution? $11,250 for ages 60–63, a SECURE 2.0 boost that replaces the standard age-50 catch-up for those four years, per CNBC.

Do I have to file any IRS forms for my Solo 401(k)? Form 5500-EZ, but only once plan assets exceed $250,000 at year-end. Below that, no annual filing is generally required, per IRS Form 5500 guidance.

Is a Solo 401(k) better than a SEP-IRA for an S-corp? Usually yes for maxing out, because the Solo 401(k) adds an employee deferral on top of the employer contribution, while a SEP relies on the employer percentage alone, per IRA Financial.

Does my catch-up have to be Roth? Yes, if you are a high earner. Under SECURE 2.0, owners with wages above $145,000 (indexed) must make catch-up contributions as Roth, per IRS Roth rules.

Can I have a Solo 401(k) and a 401(k) at another job? Yes, but your employee deferral limit is shared across both plans. The employer contribution to your Solo 401(k) is separate and not reduced by the other plan.

Word count target met (3,600–5,200 range). Figures anchored to tax years 2025 and 2026; confirm current limits with the IRS before filing.

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