Solo 401(k) for Business Owners: Contributions, Deadlines and Setup

Solo 401(k) plans are for self-employed individuals only. The eligibility bar is clear but has nuances that trip people up:

• You must have earned income from self employment. This includes net self employment income from a sole proprietorship, consulting work, or W-2 wages you pay yourself through a corporation.

• Participants must have no employees other than a spouse. If you have common law employees working more than 1,000 hours per year, you are disqualified from maintaining a solo 401(k).

• Eligible business structures include sole proprietors, single-member LLCs, S corporations, C corporations, and partnerships where only owners participate. Owner only corporations and owner only businesses of any legal form qualify.

• All businesses owned by the individual are considered related for eligibility purposes. If you own two businesses and one has eligible employees working full-time, that can affect your solo 401(k) eligibility across both.

• Eligibility includes sole proprietors and independent consultants, as well as freelancers and contract workers with no staff beyond a spouse.

A business with full-time employees cannot use a solo 401(k). If you hire a non-spouse employee in 2026 who meets the 1,000-hour threshold, you will generally need to convert to a traditional small-business retirement plan or terminate the solo 401(k) and roll assets to another qualified plan.

A spouse on payroll can participate with their own set of employee and employer contributions inside the same plan document, effectively doubling the household's total contribution capacity.

If you are unsure whether your situation qualifies, schedule a quick review call with Revolutionary Wealth before year-end.

Solo 401(k) contribution limits operate on two layers: employee salary deferrals and employer profit sharing contributions. Both are subject to annual IRS caps tied to earned income under the Internal Revenue Code.

Employee side: For the 2026 tax year, you can defer up to $24,500 in salary deferral contributions, either pre tax or as designated Roth contributions. For context, in 2023 the employee contribution limit was $22,500, and individuals aged 50 and older could contribute an additional $7,500 in catch up contributions. The limits have climbed steadily since then.

Employer side: Employer profit sharing contributions can reach up to 25% of W-2 compensation for corporate owners or roughly 20% of net self employment income for sole proprietors and single-member LLCs.

Combined totals:

• In 2023, the total contribution limit was $66,000 (plus catch-up for those 50+).

• For 2025, the total contribution limit is $70,000.

• For 2026, total contributions can reach $72,000 for those under 50.

• Catch-up contributions for those 50 and older can add $8,000 annually in 2026. Those aged 60 to 63 may qualify for an additional catch up contribution of $11,250 under SECURE 2.0 rules.

If you also participate in another employer's other retirement plan, the employee contribution limit is shared across all plans. However, employer contribution limits are generally calculated separately for each unrelated employer.

The math changes depending on how your business is structured. Here is where most owners get confused and where the details matter most.

• Sole proprietors and single-member LLCs: Your earned income is based on Schedule C net profit minus half of self employment tax and plan contributions. Employer contributions can be up to 25% of net income, but because of the way the IRS adjustment works, employer profit sharing is usually around 20% of adjusted net earnings. Self employment tax further reduces the base.

• S-corporation owners: Contributions are based on W-2 wages, not distributions. You must pay yourself a reasonable salary. Employer profit sharing contributions are generally limited to 25% of that W-2 salary. Profit distributions that bypass payroll do not count as compensation for contribution purposes.

• C-corporation owners: Similar to S-corp rules. Salary deferral and employer contributions both key off W-2 compensation.

Example: An S-corp owner paying themselves a $200,000 W-2 salary in 2026 could defer $24,500 in employee salary deferral and receive employer profit sharing contributions of 25% of compensation, or $50,000. That approaches the $72,000 cap. If over age 50, add $8,000 in catch-up, pushing the total toward $80,000.

High-income business owners should have their CPA and advisory team coordinate salary levels, distributions, and retirement contributions for optimal results. This is exactly what Revolutionary Wealth does for clients earning $500,000 and above.

There are two critical timeframes: the plan establishment deadline and the contribution funding deadlines. They are not the same, and confusing them costs people real money.

• Plan establishment: To make employee contributions for a given tax year, the solo 401(k) must be established by December 31 of that year. The adoption agreement must be completed by December 31st. The employee salary deferral election must be signed by that date, even if actual cash is contributed later.

• Funding employee deferrals: Employee deferrals should be deposited per plan rules, generally by the tax filing deadline or sooner.

• Employer contributions: Employer profit sharing contributions can usually be made up to the business's tax filing deadline for that year, including extensions. For S or C corporations, that is typically March 15 plus a six-month extension. For sole proprietors, April 15 plus extension.

Missing the December 31 establishment deadline means you permanently lose the ability to make salary deferral contributions for that tax year. Missing the employer contribution deadline forfeits that deduction entirely. This is why proactive planning with a tax advisor matters, especially for business owners with fluctuating income.

Do not wait until December to start this conversation. Book a planning call with Revolutionary Wealth well before year-end.

A solo 401(k) is a tax strategy tool as much as a retirement plan. Here is how the tax benefits stack up:

• Pre tax contributions to the employee side reduce your personal taxable income dollar for dollar. Employee contributions reduce personal taxable income in the year they are made.

• Employer contributions are typically deductible as a business expense, lowering the business's net earnings and potentially reducing income tax and self employment tax liability.

• Solo 401(k) contributions can grow tax-deferred until withdrawal. Earnings inside the account, whether from mutual funds, bonds, or other investments, are not taxed annually. This creates compounding in a tax deferred account that outpaces taxable alternatives.

• Roth contributions offer a different angle: no current tax deduction, but tax free growth and tax free qualified withdrawals in retirement. Employee contributions to a Solo 401(k) can be made on a pre-tax or Roth basis, giving you control over when you pay the tax bill.

• Strategic uses include smoothing high-income years, coordinating with other retirement accounts, and freeing cash flow for Roth conversions or a backdoor Roth IRA.

Integrated tax planning turns solo 401(k) contributions into long-term wealth, not just a short-term tax deduction.

Many small business owners weigh the solo 401(k) against a SEP IRA or other self-employed retirement plans. The differences are not cosmetic.

• A solo 401(k) allows employee contributions unlike SEP IRAs. SEP IRAs only allow employer contributions, not employee contributions. That single difference limits how much a SEP IRA holder can save at moderate income levels.

• Solo 401(k) contributions can exceed SEP IRA limits for high earners because you get both the employee deferral and the employer profit sharing contribution. A SEP IRA caps out at the employer side alone.

• SEP IRAs are simpler but offer lower contribution limits than Solo 401(k)s. If simplicity is your top priority and you earn under $100,000, a SEP might work. Above that, the solo 401(k) pulls ahead.

• SEP IRA balances are included in the pro-rata calculation for a backdoor Roth IRA conversion, making them less attractive for high earners using that strategy. Solo 401(k) plan assets generally do not trigger the same issue.

• Solo 401(k)s can offer Roth employee contributions, plan loans, and more precise year-to-year control. A Solo 401(k) allows loans up to 50% of the account balance or $50,000, whichever is less. SEP IRAs offer none of that.

For a deeper side-by-side breakdown, read our guide on Solo 401(k) vs. SEP IRA vs. Cash Balance Plan. If you currently hold a SEP IRA and are considering a rollover or backdoor Roth IRA strategy, schedule a review with our team.

Beyond basic pre tax contributions, many solo 401(k) providers now support advanced options that can reshape your long-term tax picture.

Roth solo 401(k) contributions use after tax dollars. You give up the current tax deduction in exchange for tax free qualified withdrawals in retirement. For 2026, under SECURE 2.0 rules, catch-up contributions for participants with prior-year W-2 wages exceeding $150,000 must be made as designated Roth contributions.

Some custom solo 401(k) plans allow after tax contributions above the standard employee deferral limit. When paired with an in-plan Roth conversion, this creates the mega backdoor Roth strategy, a powerful way to build Roth balances far beyond the normal Roth IRA contribution limits. Not every provider supports after tax contributions or in-plan conversions, so plan design matters.

A self directed IRA or self-directed solo 401(k) can also hold alternative investments like real estate and private equity under specific circumstances, though this adds complexity and potential account fees and maintenance fees.

Adding complexity to your plan justifies professional guidance. Revolutionary Wealth's investment management service ensures these features are evaluated in context, alongside future business exit planning and estate goals, rather than as standalone hacks.

Many professionals, physicians, and consultants have both a traditional employer 401(k) from a day job and 1099 income eligible for a solo 401(k). The coordination rules matter.

• The annual employee contribution limit ($24,500 for 2026) is shared across all 401(k) and 403(b) plans. If you max out deferrals at your day job, your solo 401(k) can only receive employer profit sharing contributions from side-business profits.

• Employer and profit sharing contributions are calculated separately for each unrelated employer's plan, subject to overall IRS rules and total addition limits.

Example: A consultant maxes out $24,500 in employee deferrals through a prior employer's 401(k). They also earn $80,000 from an independent consulting practice. Through their solo 401(k), they can make employer contributions of roughly 20% of adjusted net earnings from that practice, adding another $14,000 to $16,000 in retirement savings without exceeding any limits.

Rolling old employer plans and other retirement accounts into a solo 401(k) can consolidate investments and, in some cases, clear the way for a backdoor Roth IRA by zeroing out traditional IRA balances. If you are maxing out your 401(k) and wondering what comes next, that is where coordination with Revolutionary Wealth prevents excess contribution penalties and missed opportunities.

If your business clears $200,000 or more in annual profit, here is the honest truth: a solo 401(k) by itself probably is not doing enough for you. Once your plan contributions hit the $72,000 ceiling, every dollar of additional profit gets taxed at your full marginal rate. That is where a cash balance plan changes the math.

A cash balance plan is a type of defined benefit retirement plan that allows much larger, age-based employer contributions on top of what a solo 401(k) delivers. For owners in their 50s and 60s, annual contributions can range from $100,000 to $300,000 or more, depending on actuarial plan design, income, and proximity to retirement. According to the Tax Policy Center, cash balance plans grew from roughly 1,477 in 2001 to over 22,657 by 2020, now representing more than half of all private-sector defined benefit plans.

Cash balance contributions are employer contributions only, fully deductible to the business, and require an actuarial design tailored to the owner's age, income, and retirement goals. Contributions are based on a formula rather than discretionary year-to-year choices, which is why these plans work best for businesses with stable, consistently profitable cash flows.

If you are hitting the ceiling of your solo 401(k), explore Revolutionary Wealth's cash balance planning and schedule a design session.

Layering a cash balance plan with a solo 401(k) turns a simple retirement account into a full-scale wealth-building engine. Here is what the combination delivers:

• Dramatically higher deductible contributions. Instead of stopping at $72,000, you may shelter $200,000 or more per year in qualified plans, depending on age and plan design. That is a meaningful reduction in taxable income and income tax owed.

• Accelerated retirement savings. For owners starting late or wanting to compress decades of saving into a shorter window, the cash balance plan provides the volume that a defined contribution plan alone cannot.

• Strategic asset allocation across plans. The solo 401(k) often holds growth-oriented assets tied to your investment objectives, while the cash balance plan may use a more conservative allocation designed to meet actuarial return targets and required funding levels.

• Business exit and estate planning alignment. Properly designed combinations support future exit strategies by creating structured retirement income streams and transferring wealth into tax-advantaged vehicles before a sale or transition.

For a deeper understanding, read our complete guide for business owners on cash balance plans. The complexity of defined benefit calculations is exactly why business owners should partner with a specialized advisory firm that coordinates actuarial design, investment management, and tax strategy in one place.

Revolutionary Wealth is an independent advisory firm built around the specific needs of business owners, pre-retirees, and high-income professionals. We are not a product shop. We do not sell a solo 401(k) off a shelf and call it a day. We design coordinated strategies that account for your entity structure, cash flow, retirement timeline, and the tax picture five, ten, and twenty years out.

What makes us different for solo 401(k) and cash balance plan clients:

• Integrated planning under one roof. Tax planning, retirement planning, business exit planning, and investment management are all handled together, not farmed out to disconnected vendors. We are also a licensed insurance agency when annuity or insurance solutions make sense.

• Coordinated professional team. We work closely with actuaries, CPAs, and attorneys to design solo 401(k) and cash balance structures that fit owners earning $500,000 and above. We do not provide legal or accounting advice ourselves, but we orchestrate the team that does.

• Ongoing evaluation. We regularly help clients determine whether high contribution limits in a solo 401(k) alone are sufficient or if adding a cash balance plan better aligns with their goals, risk tolerance, and cash flow.

Whether you need a straightforward solo 401(k) or a layered strategy combining defined contribution and defined benefit plans, start with a no-pressure consultation. You can also explore our business owner services for a broader look at what we offer.

Setup is straightforward, but the details matter for compliance and maximum contributions. Here is the process:

1. Confirm eligibility. Verify you have earned income from self employment, no common law employees beyond a spouse, and that your business structure qualifies.

2. Obtain or confirm an EIN. You need an Employer Identification Number (EIN) to open a solo 401(k). If your business already has one, you are set. The EIN is issued by the IRS, the federal government agency that oversees retirement plan compliance.

3. Choose a provider that offers solo 401(k) plans. Not all custodians support Roth contributions, after tax contributions, or plan loans. Evaluate providers based on features, account fees, and whether they support the strategies you need.

4. Complete a signed adoption agreement to establish the plan. Documentation is required to open a solo 401(k) account. The adoption agreement must be executed by December 31 of the year you want to begin making maximum contributions.

5. Fund the account. Make employee deferrals and employer contributions by the applicable deadlines described above.

Annual maintenance tasks:

• Determine contribution amounts each year based on income and strategy.

• Fund the account by the tax filing deadline (including extensions).

• Keep records of all employee elections and plan contributions.

• Once total Solo 401(k) plan assets exceed $250,000, IRS Form 5500-EZ must be filed annually.

Common pitfalls include exceeding the employee contribution limit when you participate in multiple plans, miscalculating employer contributions for sole proprietors versus corporate owners, and missing the December 31 establishment deadline. Busy owners should delegate plan selection, investment management, and compliance oversight to an advisory team like Revolutionary Wealth so they can focus on running the business.

Choosing the right investments inside a solo 401(k) and any cash balance plan is just as important as choosing contribution levels. Too many owners open the account, pick a target-date fund, and never look at it again.

A unified investment strategy should span all retirement accounts and taxable accounts, accounting for risk tolerance, time horizon, required minimum distributions, future business exit plans, and withdrawing funds in the most tax-efficient sequence.

• A solo 401(k) often holds growth assets like diversified stock and bond mutual funds tied to your asset allocation targets.

• A cash balance plan may use more conservative allocations designed to meet actuarial return assumptions.

• Taxable accounts may hold tax-efficient index funds or assets you need liquid access to.

Revolutionary Wealth's investment management service centralizes portfolio design, monitoring, and rebalancing across your retirement accounts. We encourage every client to view their solo 401(k) not as an isolated account, but as one piece of a broader wealth strategy coordinated intentionally alongside every other dollar you own.