Can I Contribute 100% of My Salary to my 401k?

Watch: A full breakdown of employee, employer, and voluntary after-tax Solo 401k contribution rules for 2026.

A common question from self-employed savers is whether they can put 100% of their paycheck into their Solo 401k. The short answer: sometimes, but only up to the applicable IRS limit, and only if you have enough qualifying compensation to support it. Below, we break down the 2026 contribution rules for employee deferrals, employer profit sharing, and the Mega Backdoor Roth strategy using voluntary after-tax contributions.

What “100% of Compensation” Actually Means

The phrase “100% of compensation” is only one half of the contribution formula — it does not override the IRS’s annual dollar limit. For 2026, the employee (salary deferral) contribution limit to a 401k, including a Solo 401k, is the lesser of 100% of your eligible compensation or $24,500. That means someone earning $20,000 could potentially defer the entire amount, while someone earning $100,000 is still capped at $24,500 as an employee contribution.

Example: Jack is self-employed through an LLC taxed as an S-corporation and receives $18,000 of W-2 wages (Box 1) for 2026. Because $18,000 is below the $24,500 employee deferral limit, Jack can elect to contribute the entire $18,000 to his Solo 401k as an employee contribution — he simply doesn’t have enough compensation to reach the full $24,500.

Important: If Jack instead earned $80,000 of W-2 wages from that same S-corporation, he still cannot contribute more than $24,500 as an employee contribution. The $24,500 figure is an IRS ceiling on employee deferrals, not a percentage of an unlimited salary.

2026 Solo 401k Contribution Limits by Age

Catch-up contributions increase what you can defer as an employee if you meet the age requirements. Here is a summary of the 2026 figures:

Age Group	Employee Deferral Limit	Catch-Up Amount	Total Employee Limit	Overall 415(c) Limit*
Under 50	$24,500	$0	$24,500	$72,000
50–59, or 64+	$24,500	$8,000	$32,500	$80,000
60–63 (super catch-up)	$24,500	$11,250	$35,750	$83,250

*The overall Section 415(c) limit for 2026 is $72,000 (100% of eligible compensation, if lower), plus any applicable catch-up amount.

Catch-Up Contributions Are a Dollar-for-Dollar Requirement

To make the full catch-up amount, you need matching gross wages. A participant age 50–59 (or 64+) needs at least $32,500 of gross W-2 wages (Box 1) from the self-employed business to support the full $24,500 plus $8,000 catch-up. A participant age 60–63 needs at least $35,750 of gross wages to support the full $24,500 plus $11,250 super catch-up.

Aggregation Rules: Daytime Job Plus Solo 401k

If you work a full-time job that offers a 401k and run a self-employed business with its own Solo 401k, your employee contributions are aggregated across both plans — you cannot contribute $24,500 to each plan separately.

Example: Jack earns $18,000 of W-2 wages from his own S-corp and also works for Walmart, which offers a 401k. Jack contributes the full $18,000 as an employee contribution to his Solo 401k. He can then contribute the remaining $6,500 (to reach the $24,500 aggregate limit) to the Walmart 401k, as long as his Walmart W-2 wages support it.

Info: Employer profit sharing contributions and voluntary after-tax contributions are not subject to this aggregation rule. That means you can max out your daytime employer’s 401k and still contribute up to the full $72,000 overall limit to your Solo 401k through employer profit sharing or voluntary after-tax contributions.

S-Corp Shareholder Distributions Don’t Count

Warning: The IRS has confirmed that S-corporation shareholder distributions are not earned income for retirement plan contribution purposes — this applies to Solo 401k, SEP IRA, SIMPLE IRA, and defined benefit plans alike. Only gross W-2 wages (Box 1) count.

For example, if Jack receives $25,000 of W-2 wages and $75,000 of shareholder distributions ($100,000 total eligible compensation on paper), he can only use the $25,000 of W-2 wages to calculate his Solo 401k contributions — the $75,000 in distributions is off-limits.

Sole Proprietors and Partnerships: Adjusting Your Income Figure

Business structure changes the starting figure for your contribution calculation:

Business Structure	Starting Figure	Reduce by 1/2 SE Tax?
S-Corporation	Box 1 W-2 gross wages	No
Sole Proprietorship	Schedule C, Line 31	Yes
Partnership (LLC taxed as)	Schedule K-1, Line 14, Code A	Yes

For sole proprietors and partners, that starting figure must be reduced by one-half of self-employment tax (Social Security and Medicare) before calculating any Solo 401k contribution — employee, employer, or voluntary after-tax. This reduction does not apply to S-corporations, where the full W-2 Box 1 wages are used directly.

Contributions Don’t Reduce Payroll Taxes

Important: Employee contributions reduce taxable wages for federal income tax purposes (when made pre-tax), but they do not reduce Social Security or Medicare tax. For an LLC taxed as an S-corporation, FICA tax still applies to employee contributions, though it does not apply to employer profit sharing contributions.

Pre-Tax vs. Roth Employee Contributions

Pre-tax and Roth employee contributions share the same $24,500 limit for 2026 — it is not a separate limit for each. You can split the $24,500 however you like between the two. For example, you could contribute $14,500 pre-tax (reducing your taxable income) and $10,000 as a Roth employee contribution, totaling $24,500.

Voluntary After-Tax Contributions and the Mega Backdoor Roth

Beyond employee deferrals, many Solo 401k plans — including ours — allow voluntary after-tax contributions. These are the engine behind the Mega Backdoor Roth strategy: making voluntary after-tax contributions and immediately converting them to your Roth Solo 401k (or a Roth IRA) so the earnings grow tax-free going forward.

Contribution Type	Counts Toward	Aggregated Across Plans?	Catch-Up Eligible?
Employee (Pre-Tax or Roth)	$24,500 deferral limit	Yes	Yes
Employer Profit Sharing	$72,000 (415(c)) limit	No	No
Voluntary After-Tax (Mega Backdoor Roth)	$72,000 (415(c)) limit	No	No

Example: Jack maximizes his contributions to the Walmart 401k at $72,000 for 2026. Because voluntary after-tax contributions are not subject to aggregation rules, Jack can also contribute the full $72,000 to his Solo 401k as a voluntary after-tax contribution, as long as he reports at least $72,000 of W-2 wages from his own S-corporation.

Important: If voluntary after-tax funds are not converted right away, only the basis is tax-free when distributed — the earnings that accrued are taxable. This defeats the purpose of the strategy, so always convert voluntary after-tax funds to your Roth Solo 401k or Roth IRA promptly. Catch-up contributions can never be made as voluntary after-tax contributions.

Tracking Separate Holding Accounts

A plan that supports the Mega Backdoor Roth needs to separately track each source of funds, so you’ll typically open three holding accounts: pre-tax, Roth, and voluntary after-tax. If your spouse also participates in the plan, that’s three more accounts for a total of six — still just one Solo 401k plan overall.

Employer Roth Solo 401k Contributions

Employer Roth contributions are allowed but less commonly used, since they’re calculated as a percentage of compensation rather than dollar-for-dollar — meaning it takes more earned income to max out your Roth Solo 401k this way compared to the Mega Backdoor Roth. Employer Roth contributions are deductible on the business side but treated as a taxable in-plan conversion on the personal side, requiring a Form 1099-R. For an S-corporation, this contribution is reported on Form 1120-S, line 17.

Employer Profit Sharing Contributions

Profit sharing contributions are employer contributions, separate from employee deferrals and voluntary after-tax contributions. For an LLC taxed as an S-corporation, the employer can contribute up to 25% of W-2 wages. Without W-2 wages (or qualifying self-employment income for a sole proprietorship or partnership), no profit sharing contribution can be made — you must have earned income from self-employment activity to justify any contribution to your Solo 401k.

Choosing Where to Hold Your Funds

Info: With My Solo 401k Financial, you choose where your funds are held — a local bank, credit union, or brokerage firm such as Fidelity, Schwab, or Interactive Brokers. We never take custody of your funds.

Warning: Account-opening times vary significantly by custodian. Fidelity and Schwab typically take four to eight business days. E-Trade has taken as long as eight months in our experience since its merger with Morgan Stanley, so plan accordingly if you choose that route.

Key Takeaways

You can contribute 100% of your compensation to a 401k, including a Solo 401k, only when your compensation is below the applicable employee deferral limit. For 2026: the regular employee deferral limit is $24,500, the standard catch-up is $8,000 (age 50+), and the super catch-up is $11,250 (ages 60–63). The overall Solo 401k contribution limit is $72,000, excluding catch-up amounts, and total contributions can never exceed 100% of eligible compensation.

Employee contributions are aggregated across every 401k plan you participate in, but employer profit sharing and voluntary after-tax contributions are not. If you’re self-employed as a sole proprietor or partnership, remember to subtract one-half of self-employment tax from your earned income before calculating any contribution.

Ready to Maximize Your Solo 401k Contributions?
Whether you’re weighing employee deferrals, employer profit sharing, or the Mega Backdoor Roth, our team at My Solo 401k Financial can help you structure your Solo 401k the right way.
Next Steps: Watch more videos on our YouTube channel, read more posts on our blog, or reach out to our team directly.Get Started Today!

Remember: This information is provided for educational purposes only. Always consult with qualified tax, legal, and investment professionals before making contribution decisions with your retirement funds.