Here’s something most freelancers and independent contractors discover too late: the retirement account options available to self-employed people are dramatically more powerful than what W-2 employees get by default — and most of them aren’t using the best one. The Solo 401k, sometimes called an Individual 401k or a one-participant 401k, lets a self-employed person with $85,000 in net income potentially contribute somewhere in the range of $43,000 to $50,000 per year to retirement, depending on age and structure. That number is not a typo. And it’s fully legal.
Compare that to a standard IRA contribution limit — roughly $7,000 per year — and you start to see the gap. Even a SEP-IRA, which many accountants default to for self-employed clients, typically allows less than a Solo 401k at the same income level. If you’re earning $85,000 net from freelance work, consulting, a side business, or any other self-employment situation, understanding how a Solo 401k works isn’t optional — it’s the single highest-leverage retirement planning decision you can make.
I spent 30 years as a Warning Coordination Meteorologist with the National Weather Service, which means I spent three decades thinking about probability, risk management, and what happens when people underestimate a threat on the horizon. Freelancers and 1099 workers face a specific retirement risk that W-2 workers don’t: no employer match, no pension, no automatic enrollment, and no one checking whether you’re saving at all. The Solo 401k is one of the most effective tools available to address that gap — but only if you understand how it actually works.
What Exactly Is a Solo 401k?
A Solo 401k is a standard 401k plan designed for self-employed individuals with no full-time employees other than a spouse. If you file Schedule C income, are a single-member LLC, a sole proprietor, a freelancer, a consultant, or a 1099 contractor, you generally qualify to open one — as long as you have no employees. (Employing a spouse is the one exception; a spouse can participate in the plan.)
The reason Solo 401k contribution limits are so high is structural: as a self-employed person, you’re both the employee and the employer. That means you get to make contributions from both sides of the equation — an employee contribution (same limit as any W-2 employee’s 401k contribution) plus an employer profit-sharing contribution on top of it. Most self-employed people using a SEP-IRA only get one of those two buckets.
The Math for $85,000 in Net Self-Employment Income
The contribution calculation has a few specific steps. This is worth walking through carefully because the IRS math is slightly counterintuitive, and the numbers matter a lot at tax time.
Step 1 — Calculate net self-employment income. If your business grossed $85,000 after business expenses, you’re starting from that number. Self-employment income is what you report on Schedule C net of expenses.
Step 2 — Subtract the SE tax deduction. Self-employed people pay self-employment tax at 15.3% on net income (covering both the employee and employer halves of Social Security and Medicare). However, you can deduct half of that SE tax before calculating your retirement contribution base. At $85,000 net income, the SE tax is roughly $12,003; half of that is approximately $6,002. So your contribution base becomes $85,000 minus $6,002, or roughly $78,998.
Step 3 — Calculate the employee contribution. The employee side of a Solo 401k allows you to contribute up to 100% of your compensation — but subject to the annual 401k elective deferral limit, which has been in the range of $22,500 to $23,500 in recent years (verify the current year limit on the IRS website, as this adjusts for inflation). If you’re age 50 or older, catch-up contributions add an additional $7,500 per year. Let’s use $23,000 as a round example for the employee contribution.
Step 4 — Calculate the employer profit-sharing contribution. As the employer, you can contribute up to 25% of your net self-employment compensation (the $78,998 figure from Step 2). Twenty-five percent of $78,998 is approximately $19,750.
Step 5 — Add them together. Employee contribution ($23,000) plus employer contribution ($19,750) equals approximately $42,750 in total Solo 401k contributions at $85,000 in net income — before any catch-up contributions. If you’re 50 or older, add another $7,500 to the employee side, bringing the total to roughly $50,250.
The overall cap on combined contributions is set by the IRS each year (historically around $66,000 to $69,000 for those under 50; verify current limits at IRS.gov). At $85,000 net income, you won’t hit that ceiling — your profit-sharing contribution caps out at the 25% of net earnings calculation above.
Solo 401k vs. SEP-IRA at the Same Income
A SEP-IRA, the other common retirement account for self-employed people, only allows the employer side — 25% of net self-employment compensation. At $85,000 net income, that’s the same $19,750 calculated above. No employee contribution on top of it.
The Solo 401k at the same income: $42,750 (or $50,250 with catch-up). The SEP-IRA at the same income: $19,750. That’s a difference of roughly $23,000 in tax-deductible contributions per year. At a 22% federal tax bracket, that’s approximately $5,060 in federal taxes you’re not paying this year. Over a 10-year period with even modest investment returns, the compounding effect of that additional $23,000 per year is substantial.
The SEP-IRA has a few advantages worth noting: it’s simpler to set up, has fewer administrative requirements, and has a later contribution deadline (you can open and fund it at tax filing time, even with an extension, for the prior tax year). The Solo 401k requires the plan to be established before December 31 of the tax year you want to deduct contributions for — though you can fund it up until your tax filing deadline including extensions. If you discover Solo 401k in February while doing your taxes, you likely missed the window for that prior year.
Traditional vs. Roth Solo 401k — Which Structure Makes More Sense?
Like a regular 401k, Solo 401k plans can often be structured as traditional (pre-tax contributions, taxes paid on withdrawal) or Roth (after-tax contributions, tax-free growth and withdrawal). The employee elective deferral portion can typically be designated as Roth; the employer profit-sharing portion is generally required to be pre-tax.
The right choice depends on your current tax bracket versus your expected retirement tax bracket. For a self-employed person earning $85,000 in net income, you’re likely in the 22% federal bracket (exact bracket depends on deductions, filing status, and other factors). If you expect to be in a lower bracket in retirement — which many people are after required minimum distributions start — the traditional pre-tax route reduces your current-year tax bill and defers the tax. If you expect significant growth in income or assets, or you want tax-free income in retirement to manage Medicare IRMAA surcharges and bracket management, the Roth side may make more sense for at least part of the contribution.
The bracket-management interplay between traditional and Roth contributions — and why the right answer often isn’t all-or-nothing in either direction — is explored more fully in the broader guide to Roth conversion strategy at 58 and how much to convert per year based on tax bracket. The same logic applies to self-employed workers building their retirement allocation: the question is always which bracket you’re filling at what cost.
Where to Open a Solo 401k
Several major brokerage firms offer Solo 401k plans at no cost: Fidelity, Charles Schwab, and Vanguard are the most common choices for straightforward setups. Fidelity’s Self-Employed 401k plan allows both traditional and Roth contributions. Schwab’s Individual 401k is similar. Both are free to open and have no annual fees for basic accounts.
If you want more flexibility — specifically the ability to make after-tax contributions and then convert them to Roth (the "mega backdoor Roth" strategy), or to invest in alternative assets like real estate or private equity — you’ll need a self-directed Solo 401k through a specialized provider. These are more complex and often come with setup and annual maintenance fees of $300 to $800 or more. For most freelancers earning $85,000, a standard no-fee Solo 401k at Fidelity or Schwab is the right starting point. The complexity of a self-directed plan isn’t warranted unless you have specific investment goals that require it.
The HSA Connection — Stacking Your Tax Advantages
One of the most underused strategies for self-employed people: pairing a Solo 401k with a Health Savings Account. If you’re on a qualifying high-deductible health plan (which many self-employed people choose specifically for the lower premiums), you can contribute to an HSA on top of your Solo 401k — and the HSA contribution is also fully deductible. HSA contribution limits for an individual run around $4,000 to $4,300 per year; for a family, $8,000 to $8,500 (verify current limits on IRS.gov — these adjust annually).
The HSA triple tax advantage — deductible going in, grows tax-free, tax-free for qualified medical expenses — makes it one of the most tax-efficient accounts available to anyone, but especially to self-employed people who are already paying the full freight of self-employment taxes without employer benefits. Whether to max the HSA before or alongside the Solo 401k depends on your cash flow and healthcare situation, and the full breakdown of that trade-off is in the detailed analysis of whether to max your HSA before your Roth IRA if you’re on a high-deductible plan. The same decision tree applies to Solo 401k holders.
Five Common Mistakes Self-Employed People Make With Solo 401ks
1. Missing the December 31 establishment deadline. The plan must exist before December 31 of the year you want to deduct contributions for. Opening it in February is too late for the prior year. Set a calendar reminder in November.
2. Defaulting to a SEP-IRA because an accountant or bank suggested it first. SEP-IRAs are simpler but allow significantly smaller contributions at moderate income levels. If you’re earning more than about $45,000 in net self-employment income, the Solo 401k is almost always the better choice by a wide margin. Run the math or ask your accountant to run the comparison specifically.
3. Contributing as an employee only (missing the employer side). Some self-employed people contribute the $23,000 employee deferral and stop there, unaware they can also add the employer profit-sharing contribution on top. This is a significant missed opportunity at any income level above roughly $30,000.
4. Forgetting to file Form 5500-EZ once the plan balance exceeds $250,000. Plans with assets over $250,000 at the end of the plan year are required to file an annual return. This is not a complex filing, but missing it triggers penalties. Set a reminder and track your balance.
5. Treating all income as eligible without checking the rules. Solo 401k contributions must be based on net self-employment income — not gross revenue, not W-2 income from a separate employer. If you have a W-2 job in addition to freelance work, your employee elective deferral limit is shared across all plans. You can’t contribute $23,000 to your W-2 employer’s 401k and another $23,000 to your Solo 401k — the employee deferral limit applies per person, not per plan.
The Self-Employed Retirement Stack — How It Fits Together
For a self-employed person earning $85,000, a solid retirement stack might look like this (in rough priority order, subject to your specific cash flow):
- Solo 401k employee contribution: up to $23,000+ (pre-tax or Roth, established by December 31)
- HSA contribution: up to $4,000+ if on an HDHP (triple tax advantage, deductible from gross income)
- Solo 401k employer profit-sharing contribution: up to ~$19,750 (pre-tax, filed by tax deadline with extensions)
- Roth IRA contribution if income-eligible: up to $7,000 after maxing the above
The total potential tax-advantaged savings in this stack at $85,000 net income: roughly $54,000 per year before any income eligibility phase-outs. For comparison, a W-2 employee at the same income who maxes their employer’s 401k and contributes to an IRA caps out around $30,000. The self-employed retirement advantage, when used correctly, is significant.
Building the full picture of your retirement strategy as a self-employed person — how your solo savings rate stacks against benchmarks, what your projected income in retirement might look like, and whether your current trajectory will actually get you where you need to go — is the work the broader guide to financial planning for self-employed individuals covers in detail. Start there for the comprehensive framework; then come back to the Solo 401k as the specific vehicle for the tax-advantaged savings piece.
The Bottom Line
At $85,000 in net self-employment income, a Solo 401k can shelter approximately $42,750 per year from income tax before catch-up contributions, versus about $19,750 with a SEP-IRA — a difference of roughly $23,000 per year. Over a decade, that compounding difference is real money. The Solo 401k is not complex once you understand the two-bucket structure, but it does require establishing the plan by December 31 and filing Form 5500-EZ once balances exceed $250,000.
If you’re self-employed and don’t currently have a retirement plan, opening a Solo 401k at Fidelity or Schwab today takes about 20 minutes and costs nothing. If you already have a SEP-IRA and have been earning above $50,000 in net income for more than a year, it’s worth running the comparison to see how much you’ve left on the table — and whether switching makes sense going forward. For deeper reading on the mechanics of retirement account sequencing and which accounts to fill in which order, books on self-employed retirement planning and Solo 401k strategy provide the full framework. The landmark guide to building sustainable retirement income for people without a pension or traditional employer plan, Wade Pfau’s Retirement Planning Guidebook, covers the withdrawal-side strategy you’ll eventually need once the accumulation phase ends. And for anyone who’s still skeptical that $23,000 per year compounding over 20 years at average market returns actually matters: run it in a compound interest calculator — books on compound interest and long-term wealth building make the math visceral in a way a spreadsheet sometimes doesn’t. The Solo 401k is one of the quietest advantages available to self-employed Americans. Most of them aren’t using it.