Solo 401(k) Contribution Calculator 2026 (Self-Employed 401k)
The 2026 Solo 401(k) contribution limit is $72,000 (§415(c)) plus up to $8,000 catch-up (age 50–59 or 64+) or $11,250 super catch-up (age 60–63), for a maximum of $83,250. Employee deferrals are capped at $24,500 (§402(g)), shared across all 401(k) plans. Sole proprietors use 20% of net SE earnings; S-corp owners use 25% of W-2 wages, both capped at $360,000 compensation. Source: IRS Notice 2025-67.
For Reference Only
These figures are estimates based on standard formulas. Your actual numbers will depend on your situation and elections. This tool is for informational purposes only and is not tax or financial advice.
Calculation Results
Base deferral
20% of net SE earnings
How this is calculated
SE tax (15.3% × net profit): $15,300
½ SE tax deduction: $7,650
Adjusted net earnings: $92,350
Employer contribution (20% × adjusted): $18,470
§415(c) base cap: $72,000
Source: IRS Notice 2025-67 · IRS Pub 560
Put This Number to Work
A calculator result is only useful if you act on it. Use these figures as a baseline to model scenarios and optimize your financial plan.
⚡ 2026 Solo 401(k) Limits — Quick Reference
| Contribution Type | 2026 Limit | 2025 Limit | Change |
|---|---|---|---|
| Employee deferral (§402(g)) | $24,500 | $23,500 | +$1,000 |
| Catch-up age 50–59 & 64+ | $8,000 | $7,500 | +$500 |
| Super catch-up age 60–63 (SECURE 2.0) | $11,250 | $11,250 | Unchanged |
| Annual additions cap (§415(c)) excl. catch-up | $72,000 | $70,000 | +$2,000 |
| Max total age 50–59 or 64+ | $80,000 | $77,500 | +$2,500 |
| Max total age 60–63 | $83,250 | $81,250 | +$2,000 |
| Compensation cap (§401(a)(17)) | $360,000 | $350,000 | +$10,000 |
Source: IRS Notice 2025-67 · IRS IR-2025-111 (Nov 13, 2025)
Trying to maximize your retirement savings as a business owner? A Solo 401(k)—also known as a solo k or self-employed 401(k)—offers the highest contribution limits of any individual retirement plan. Use our solo 401k contribution calculator to determine your exact maximum allowable contribution for 2026 based on your business structure and net compensation.
Solo 401(k) = Individual 401(k) = i401k = Solo-k = Uni-K = One-Participant 401(k)
All of those names describe the same IRS plan: the one-participant 401(k) plan. Financial institutions use different marketing labels — Fidelity calls it a "Self-Employed 401(k)," Vanguard calls it an "Individual 401(k)," and Charles Schwab calls it a "Personal 401(k)" — but the IRS rules are identical regardless of what your brokerage calls it. For SEO purposes, if you searched for "solo k contribution limits," "individual 401k calculator," "i401k contribution calculator," or "uni-401k limits," you have found the right page.
🧮 How Self-Employed 401(k) Limits Work
Because you are both the employee and the employer in your solo k plan, you get to contribute in two separate ways:
- Employee Elective Deferrals: For 2026, you can contribute up to $24,500 as an employee (or up to $32,500 if you are age 50–59 or 64+, and $35,750 for ages 60–63 via the SECURE 2.0 super catch-up).
- Employer Profit-Sharing: As the business owner, you can contribute an additional 20% of your net earnings (if you are a sole proprietor) or 25% of your W-2 compensation (if you are an S-Corp), capped at $360,000 compensation.
The combined total across both contribution types cannot exceed $72,000 for 2026 (not counting catch-up contributions), per IRS Notice 2025-67 and IRS Publication 560.
📐 The Formula
Employee Deferral: Up to $24,500 (2026 base)
Age 50–59 or 64+: Up to $32,500 (+ $8,000 catch-up)
Age 60–63: Up to $35,750 (+ $11,250 SECURE 2.0 super catch-up)
Employer Contribution (Sole Prop): 20% of (Net Profit − Half SE Tax), max $360k comp
Employer Contribution (S-Corp): 25% of W-2 Salary from the S-Corp, max $360k comp
Total Limit: Lesser of Employee + Employer, or:
$72,000 (under 50) | $80,000 (age 50–59 or 64+) | $83,250 (age 60–63)Source: IRS Notice 2025-67; IRS Publication 560 (2026 edition)
📊 Step-by-Step Worked Examples (2026)
These are illustrative examples only. Numbers rounded to the nearest dollar. Verify with a tax professional for your situation.
Example 1 — Sole Proprietor, Age 42, $80,000 Net Profit
- SE tax: 15.3% × $80,000 = $12,240
- ½ SE tax deduction: $12,240 ÷ 2 = $6,120
- Adjusted net earnings: $80,000 − $6,120 = $73,880
- Employer contribution (20%): 20% × $73,880 = $14,776
- Employee deferral (base): $24,500
- Total: $24,500 + $14,776 = $39,276 (well under $72,000 cap) ✓
- SEP IRA comparison on same income: $14,776 employer-only
- Solo 401(k) advantage: +$24,500
Example 2 — S-Corp Owner, Age 44, $120,000 W-2 Salary
- Employer contribution (25% of W-2): 25% × $120,000 = $30,000
- Employee deferral (base): $24,500
- Total: $30,000 + $24,500 = $54,500 (under $72,000 cap) ✓
- Federal tax savings at 24% rate: $54,500 × 24% ≈ $13,080
Note: employer contribution is a business deduction on the S-corp return; employee deferral reduces personal W-2 income.
Example 3 — Sole Proprietor, Age 52, $100,000 Net Profit
- ½ SE tax deduction ≈ $7,065; adjusted net = $92,935
- Employer (20%): 20% × $92,935 = $18,587
- Employee deferral base: $24,500
- Age 50–59 catch-up: +$8,000
- Total: $24,500 + $8,000 + $18,587 = $51,087 (under $80,000 catch-up cap) ✓
Example 4 — Sole Proprietor, Age 61, $150,000 Net Profit (Super Catch-Up)
- ½ SE tax deduction ≈ $10,597; adjusted net = $139,403
- Employer (20%): 20% × $139,403 = $27,881
- Employee deferral base: $24,500
- Ages 60–63 SECURE 2.0 super catch-up: +$11,250
- Total: $24,500 + $11,250 + $27,881 = $63,631, capped at $83,250
- Final total: $63,631 ✓ (plan document must allow super catch-up)
Example 5 — Side Business + Day-Job 401(k), Age 38
Full-time employee who already contributed $15,000 to their employer's 401(k); also runs a freelance business with $60,000 net profit.
- §402(g) deferral limit: $24,500 total across all plans
- Already used at day job: $15,000
- Remaining Solo 401(k) employee deferral: $24,500 − $15,000 = $9,500
- ½ SE tax ≈ $4,239; adjusted net = $55,761
- Employer (20%): 20% × $55,761 = $11,152 (employer side is NOT shared)
- Total Solo 401(k) contribution: $9,500 + $11,152 = $20,652
🏢 S-Corp Owner: A Separate Calculation
If you own an S-corporation, the employer contribution math is different — and actually simpler — than for sole proprietors. Because the S-corp pays you a W-2 salary, the 25%-of-compensation rate applies directly to your salary without any self-employment tax adjustment. No conversion factor needed.
Worked Example: S-Corp Owner, Age 44, W-2 Salary = $120,000
- Employee elective deferral: $24,500
- Employer profit-sharing (25% × $120,000): $30,000
- Total Solo 401(k) contribution: $54,500 (well under the $72,000 combined cap)
- Federal income tax deduction: $54,500 × assumed 24% rate ≈ $13,080 saved
Note: The S-corp's employer contribution of $30,000 is a business deduction on the corporate return. The employee deferral is deducted on your personal W-2. Neither reduces your S-corp FICA (Social Security/Medicare) wages.
Contrast this with a sole proprietor on the same $120,000 gross income: after deducting half of self-employment tax (~$8,478), net adjusted earnings ≈ $111,522. Employer contribution at 20% = $22,304. Total = $24,500 + $22,304 = $46,804 — roughly $7,700 less than the S-corp version at the same income level, primarily because the S-corp owner avoids the SE tax adjustment.
Example: Sole Proprietor vs. S-Corp Contributions (Age 44, $100,000 income)
Assuming $100,000 in net business income, under 50.
- As a Sole Proprietor: Net adjusted self-employment income (after deducting half of SE tax ≈ $7,065) is roughly $92,935.
- Employee deferral: $24,500
- Employer contribution (20% × $92,935): $18,587
- Total Solo 401k Contribution: $43,087
- As an S-Corp Owner (W-2 salary of $100,000):
- Employee deferral: $24,500
- Employer contribution (25% × $100,000): $25,000
- Total Solo 401k Contribution: $49,500
📅 Solo 401(k) Contribution Deadlines for 2026
| Action | Deadline | Notes |
|---|---|---|
| Employee deferral election (written) | Dec 31, 2026 | Must be in writing before year-end; cannot be made retroactively |
| New plan adoption (existing businesses) | Dec 31, 2026 | Plan documents must be signed by Dec 31; SECURE 1.0 |
| Employer profit-sharing contribution | Tax return due date incl. extensions | Oct 15, 2027 for sole props; Mar 15, 2027 for S-corps (Sept 15 with extension) |
| SECURE 2.0 §317 — new sole prop plan, year 1 only | Apr 15, 2027 (no extension) | Employee deferrals allowed until unextended due date — first year of the plan only. S-corps NOT eligible for this exception. |
| Form 5500-EZ (assets > $250,000) | July 31, 2027 | Extendable with Form 5558. Also required on plan termination. |
🔄 Roth Solo 401(k): How It Works in 2026
A Solo 401(k) can accept Roth (after-tax) employee deferrals if the plan document allows it. The tax treatment differs from traditional pre-tax contributions: Roth contributions do not reduce your current taxable income, but qualified withdrawals in retirement are completely tax-free.
Key 2026 Roth Facts
- Roth and traditional deferrals share the same $24,500 §402(g) limit — you cannot do $24,500 Roth plus $24,500 traditional.
- Employer profit-sharing contributions are always pre-tax; there is no Roth employer contribution in a standard Solo 401(k).
- Your plan document must explicitly allow Roth deferrals. Most major providers (Fidelity, Schwab) do; Vanguard's prototype plan does not offer Roth as of this writing.
- Roth accounts inside a 401(k) are subject to Required Minimum Distributions (RMDs) — unlike a Roth IRA — unless you roll them to a Roth IRA before age 73.
⚠️ 2026: Mandatory Roth Catch-Up Rule (SECURE 2.0 §603)
Effective January 1, 2026, if your prior-year FICA wages from the plan sponsor exceeded $150,000 (based on your 2025 W-2 wages), ALL catch-up contributions must be designated Roth — you cannot make them as pre-tax.
| Entity Type | 2025 Wages > $150k? | Mandatory Roth Catch-Up? |
|---|---|---|
| S-Corp owner (W-2 salary) | Yes | Yes — all catch-up contributions must be Roth |
| S-Corp owner (W-2 salary) | No | No — may choose pre-tax or Roth |
| Sole proprietor / SMLLC | N/A (no W-2) | Not subject to this rule |
| Partner in partnership | N/A (no W-2) | Not subject to this rule |
Source: SECURE 2.0 §603; final IRS regulations (effective Jan 1, 2026). The transition period was not extended beyond 2025.
💑 Spouse / Married Couple Solo 401(k)
One of the most underutilized features of the Solo 401(k) is the spousal contribution. If your spouse earns genuine compensation from your business — either as a documented employee or as a co-owner — they are entitled to their own independent Solo 401(k) contribution limit. The limits do not merge into a shared pool; each spouse contributes separately under their own name.
2026 Combined Household Ceiling
- Both spouses under 50: up to $144,000 combined ($72,000 × 2)
- Both spouses age 50–59 or 64+: up to $160,000 combined ($80,000 × 2)
- Both spouses age 60–63: up to $166,500 combined ($83,250 × 2)
Requirements: the spouse must have documented, reasonable compensation from the business; the plan document must allow spouse-employee participation; payroll records must support it.
This is especially powerful for couples who both work in the same business and want to aggressively shelter income. At a 22% tax rate, sheltering $144,000 instead of $72,000 represents over $15,800 in additional immediate federal tax savings.
✅ Who Is Eligible for a Solo 401(k)?
✓ Eligible
- Self-employed sole proprietors (Schedule C filers)
- Single-member LLC owners treated as sole proprietors
- S-corp or C-corp owners who pay themselves a W-2 salary
- Partners in a partnership who receive self-employment income
- Spouses who earn compensation from the business
- Side-gig owners with self-employment income (even if employed full-time elsewhere)
✗ Not Eligible
- Businesses with common-law employees (other than a spouse) who meet coverage requirements
- Individuals with no self-employment income
- Passive investors with no earned income from the business
If you hire employees who meet the plan's eligibility requirements, you generally must convert to a regular 401(k) plan or adopt a different plan type.
⚖️ Solo 401(k) vs. SEP IRA: Full Comparison
This is one of the highest-searched comparisons for the self-employed. Here is the full picture:
| Feature | Solo 401(k) | SEP IRA | SIMPLE IRA |
|---|---|---|---|
| 2026 max contribution | $72,000 ($80,000/$83,250 w/ catch-up) | $72,000 (employer-only, no catch-up) | $17,000 + $3,500 catch-up |
| Employee deferral | ✓ Yes ($24,500 base) | ✗ No | ✓ Yes ($17,000) |
| Catch-up contributions | ✓ $8,000 (50+) / $11,250 (60–63) | ✗ None | $3,500 (50+) |
| Roth option | ✓ Yes (if plan allows) | ✗ No | Some plans |
| Mega backdoor Roth | ✓ Yes (if plan allows) | ✗ No | ✗ No |
| Plan loans | ✓ Up to 50% / $50,000 | ✗ No | ✗ No |
| Annual IRS filing | Form 5500-EZ if assets > $250k | ✓ None | ✓ None |
| Employees allowed | Owner + spouse only | ✓ Any employees | ✓ Any employees |
| Who wins at low income (<$50k)? | ✓ Solo 401(k) by wide margin | SEP far smaller | Moderate |
| Simplicity | Moderate (plan docs required) | ✓ Very simple | Moderate |
Verdict: the Solo 401(k) almost always wins on maximum contribution room, especially for anyone under $288k of self-employment income. The SEP IRA's simplicity advantage matters mainly to solopreneurs who value zero administrative overhead over every possible dollar of tax deferral.
🚫 Common Solo 401(k) Mistakes to Avoid
Missing the December 31 deferral election deadline
You cannot retroactively elect a salary deferral after December 31. If you miss the written election deadline, you lose the entire employee deferral for that year. The employer profit-sharing contribution has a later deadline — but the deferral does not.
Ignoring the shared §402(g) deferral limit
The $24,500 employee deferral limit is shared across ALL 401(k) and 403(b) plans you participate in. If you contributed to a day-job 401(k), that amount counts against your Solo 401(k) employee deferral. Over-contributing triggers a 6% excise tax.
Forgetting Form 5500-EZ at the $250,000 threshold
Once your plan assets exceed $250,000 at December 31, you are required to file Form 5500-EZ by July 31 of the following year. Missing this filing can result in penalties of up to $250/day.
Applying 20% to gross profit instead of adjusted net earnings
Sole proprietors must first deduct half of self-employment tax before applying the 20% employer rate. Using gross net profit (without the SE tax adjustment) overstates the allowable employer contribution.
Applying 25% to S-corp net income instead of W-2 salary
S-corp owners' employer contribution is 25% of their W-2 salary from the corporation — not 25% of the S-corp's net income or their total distribution. S-corp distributions (above W-2 salary) do not count as compensation for this calculation.
Not verifying plan document support for Roth or super catch-up
Roth deferrals and the ages 60–63 super catch-up are optional plan features — your plan document must explicitly allow them. Before contributing under either provision, confirm with your provider that your plan document supports it.
🏦 Solo 401(k) Providers
Several major brokerages offer free Solo 401(k) prototype plan documents. Key factors to consider when choosing a provider:
| Provider | Plan Cost | Roth Deferrals | Super Catch-Up (60–63) | 5500-EZ Help |
|---|---|---|---|---|
| Fidelity | Free | ✓ Yes | Verify with provider | Not provided |
| Charles Schwab | Free | ✓ Yes | Verify with provider | Not provided |
| Vanguard | Free | ✗ Not available | ✗ Not available | Not provided |
| TD Ameritrade (Schwab) | Free | ✓ Yes | Verify with provider | Not provided |
| Self-Directed Custodians | Fees vary | Varies by plan doc | Varies by plan doc | Some offer help |
Provider features change. Always verify Roth availability, super catch-up support, and Form 5500-EZ assistance directly with your provider before adopting a plan. This table is for general reference only.
👤 Who Should Use This Calculator?
- Freelancers, consultants, and independent contractors earning income on a 1099 basis
- Sole proprietors who file a Schedule C and have no full-time W-2 employees
- Business owners who have structured themselves as an S-Corp and want to optimize contributions through their W-2 salary and profit distributions
- High-income self-employed individuals who have maxed out a SEP IRA and want to compare whether a Solo 401(k) would allow larger contributions
- Married couples who both work in the same business and want to maximize household retirement contributions
🛠️ How to Use This Calculator
- Enter Net Business Profit / W-2 Salary: For sole proprietors, this is your Schedule C net profit. For S-Corp owners, enter your W-2 salary paid by the corporation (not distributions).
- Enter your age: The IRS allows an $8,000 catch-up for ages 50–59 and 64+, and a larger $11,250 "super catch-up" for ages 60–63 under SECURE 2.0. The calculator applies the correct amount automatically.
- Select business type: Sole Proprietors and single-member LLCs use the effective 20% employer rate. S-Corp owners use the flat 25% of W-2 salary rate.
- Enter day-job deferrals: If you already contributed to an employer's 401(k) this year, enter that amount. The calculator reduces your Solo 401(k) employee deferral room accordingly.
- Toggle spouse: If your spouse works in the business, enable the spouse toggle to see the combined household limit.
- Review results: The calculator shows your maximum employee deferral, employer profit-sharing, catch-up, and combined total — the most you can legally shelter this year.
💡 Real-World Comparison: Solo 401(k) vs. SEP IRA
Maria is a freelance graphic designer earning $80,000 in net profit for 2026. She is 38 years old and wants to maximize her retirement savings.
SEP IRA option: effective rate ≈ 20% of net self-employment income. Net earnings after half SE-tax deduction ≈ $74,208. SEP IRA max ≈ 20% × $74,208 = $14,842.
Solo 401(k) option: $24,500 employee deferral + $14,842 employer contribution = approximately $39,342 total.
By using a Solo 401(k) instead of a SEP IRA, Maria shelters an additional $24,500 from federal taxes. At a 22% marginal rate, that is over $5,390 in immediate tax savings — plus the compounding growth advantage of that extra money staying invested for decades.
🔮 2027 Limits Outlook
The IRS typically announces the following year's retirement plan limits in late October or mid-November. As of October 29, 2026, the 2027 limits have not yet been officially announced.
Various projections suggest the employee deferral limit could rise to approximately $25,500, but these are estimates only — not official figures. Do not rely on projected 2027 limits for tax planning until the IRS makes an official announcement. This calculator and the related blog post will be updated immediately upon the official IRS announcement. All limits are stored in a single config file (solo401kLimits.js) for a one-location update.
📖 Want the full deep-dive? Read our Complete Guide to Solo 401(k) Contribution Limits 2026 — covering all IRS rules, deadlines, worked examples, and comparison tables.
⚠️ Limitations of This Calculator
- This calculator assumes you have no other employer-sponsored plan. If you also have a W-2 job with a 401(k), your combined employee deferrals across all plans cannot exceed $24,500 (or the applicable catch-up limit) for 2026. Use the "day-job deferrals" field to adjust.
- The Solo 401(k) is only available to businesses with no full-time employees other than the owner and their spouse. Different plan rules may apply if you hire eligible employees.
- This calculator does not account for state-level taxes or state-specific retirement plan rules.
- Contribution deadlines matter: employee deferrals must be elected before December 31st for the tax year, while employer contributions can be made up to the tax filing deadline (including extensions).
- The $360,000 compensation cap applies to both the employer contribution calculation and the combined limit — high earners should note this ceiling.
- The super catch-up (ages 60–63) requires your plan document to explicitly allow it — confirm with your provider.
Last updated: October 29, 2026 | Tax year 2026 | All 2026 contribution limits sourced from IRS Notice 2025-67 and IRS Publication 560. SECURE 2.0 super catch-up per SECURE 2.0 §109; mandatory Roth catch-up per SECURE 2.0 §603. Always consult a licensed CPA or ERISA attorney for tax advice specific to your situation. This tool is for educational and informational purposes only and does not constitute tax, legal, or financial advice.
Frequently Asked Questions
Authoritative answers to common questions about this calculation
Q1.What is the Solo 401(k) contribution limit for 2026?
Q2.What is the Solo 401(k) contribution deadline for 2026?
Q3.Can I do a mega backdoor Roth with a Solo 401(k)?
Q4.How much can I contribute to a Solo 401(k) if I only made $30,000?
Q5.Is a Solo 401(k) better than a SEP IRA for an S-corp owner?
Q6.Can my spouse also contribute to my Solo 401(k)?
Q7.Can I open a Solo 401(k) if I have a day job with a 401(k)?
Q8.What is the Roth Solo 401(k) and how does it work?
Q9.Does a Solo 401(k) require annual IRS filings?
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For 2026, the Solo 401(k) combined contribution limit is $72,000 ($80,000 age 50+, $83,250 age 60-63). Our free calculator shows your exact maximum based on your income, age, and business type. This guide covers the 20% sole-proprietor rule vs. 25% S-corp rule, the spousal doubling strategy, mega backdoor Roth, step-by-step plan setup, and a full FAQ. All limits from IRS Notice 2025-67 and IRS Publication 560.