Sep Ira Solo 401k Simple

SEP IRA vs. Solo 401(k) vs. SIMPLE: Choosing Your Retirement Account

Self-employed workers and small business owners without employees have access to retirement accounts that are more powerful than the standard IRA—with contribution limits that dwarf the $7,000 annual IRA ceiling. The three primary options are the SEP IRA, the Solo 401(k), and the SIMPLE IRA. Each has a different contribution structure, different administrative requirements, and different suitability depending on income level, business structure, and whether you have employees.

Choosing correctly is a meaningful financial decision: the gap between the wrong account and the right one can mean $10,000 to $40,000 in additional annual tax-deductible contributions, depending on your net self-employment income.

THE SEP IRA: SIMPLE AND EMPLOYER-FUNDED

The Simplified Employee Pension IRA (SEP IRA) is the easiest self-employed retirement account to establish and maintain. There is no annual IRS filing requirement for the employer (unlike the Solo 401(k), which requires Form 5500-EZ once assets exceed $250,000). The account is opened at any brokerage and accepts contributions up to the tax-filing deadline plus extensions—providing maximum flexibility for year-end tax planning.

Contribution limit: The lesser of 25% of net self-employment income (for sole proprietors, this means 25% of net earnings from self-employment after deducting half of SE tax) or $69,000 in 2024.

For a sole proprietor with $200,000 in net Schedule C income:

Step 1: Deduct half of SE tax: approximately $14,130 (SE tax on $200,000 is approximately $28,260; half = $14,130)

Step 2: Net earnings for SEP calculation: $200,000 - $14,130 = $185,870

Step 3: 25% of $185,870 = $46,468

Maximum SEP IRA contribution at this income level: $46,468.

The SEP IRA's limitation: contributions can only come from the employer side. There is no "employee" elective deferral component. This matters because employer-only contributions are calculated as a fixed percentage of net earnings—you cannot contribute a flat dollar amount above that percentage, regardless of how much you want to save.

At lower income levels, the SEP's 25% employer-only formula produces smaller contributions than the Solo 401(k) allows. A sole proprietor earning $50,000 in net self-employment income can contribute approximately $9,283 to a SEP IRA, while the Solo 401(k) allows significantly more—as explained below.

The SEP IRA is also straightforwardly employee-friendly: if you have or later add employees, you must make the same percentage contribution for all eligible employees as you make for yourself. A business owner who contributes 20% of their own compensation to a SEP IRA must contribute 20% of each eligible employee's compensation as well. This makes SEP IRAs practical primarily for solo operators with no employees.

THE SOLO 401(K): MORE POWERFUL AT LOWER INCOMES

The Solo 401(k)—also called an Individual 401(k), Self-Employed 401(k), or i401(k)—is available to self-employed individuals and business owners with no full-time employees other than a spouse. It functions like a traditional employer 401(k) but is designed for one-person (or spousal) operations.

The Solo 401(k) has two separate contribution components:

Employee elective deferrals: Up to $23,000 in 2024 ($30,500 if age 50 or older). This is the same limit as a corporate 401(k). As the business owner, you wear both the employer and employee hats, so you can contribute this full amount as the "employee"—subject to your net self-employment income not being lower than this amount.

Employer profit-sharing contributions: Up to 25% of net self-employment earnings (calculated the same way as SEP IRA), up to the total 415 limit of $69,000.

Combined limit: $69,000 in 2024 ($76,500 if 50+), encompassing both components.

The power at lower incomes: The employee deferral component allows contributions that the SEP IRA cannot match when income is modest.

A sole proprietor with $60,000 in net self-employment income:

SEP IRA maximum: approximately $11,184 (25% of net earnings after SE tax deduction)

Solo 401(k) maximum: - Employee deferral: $23,000 (limited to net earnings, which exceed $23,000 here)

- Employer contribution: 25% of net earnings after SE tax adjustment ≈ $11,184

- Total: $34,184

At $60,000 in income, the Solo 401(k) allows $34,184 in contributions versus the SEP IRA's $11,184—a $23,000 difference, all tax-deductible.

At higher incomes, the gap narrows and eventually disappears. Once the employer component alone reaches $46,000 (at approximately $200,000 in net income), the SEP IRA and Solo 401(k) produce similar maximum contributions (since the employee deferral in the Solo 401(k) is capped at $23,000 and the employer component at 25%/$46,000).

For most self-employed workers with net income below $200,000, the Solo 401(k) allows significantly higher tax-deductible contributions.

The tradeoff: administrative complexity. A Solo 401(k) must be established with a provider that offers them—Fidelity, Vanguard, Schwab, and TD Ameritrade all offer no-cost Solo 401(k) plans with good investment options. The plan document must be adopted by December 31 of the year for which you want to make contributions (unlike the SEP IRA, which can be established up to the tax-filing deadline). Once assets exceed $250,000, Form 5500-EZ must be filed annually with the IRS—a straightforward form but one that adds an annual task.

The Solo 401(k) also permits Roth contributions if the plan document allows it—subject to the same income limits as the Roth 401(k) at employers. This option doesn't exist in a SEP IRA.

If you have employees other than a spouse, you cannot use a Solo 401(k). Adding even one part-time employee (above a certain hours threshold) converts it to a regular 401(k) subject to full ERISA compliance, testing, and reporting requirements—a fundamentally different administrative burden.

THE SIMPLE IRA: FOR BUSINESSES WITH EMPLOYEES

The SIMPLE IRA (Savings Incentive Match Plan for Employees) is designed for businesses with 100 or fewer employees. It is not primarily a self-employed vehicle—the SIMPLE IRA is most useful when a small business has employees it wants to offer retirement benefits.

Employee contribution limit: $16,000 in 2024 ($19,500 for those age 50+).

Employer mandatory contribution: Either a dollar-for-dollar match of employee contributions up to 3% of compensation, or a flat 2% non-elective contribution to all eligible employees regardless of whether they contribute.

The SIMPLE IRA's employer contribution is mandatory—it must be made for all eligible employees in every year the SIMPLE IRA is maintained. This requirement makes it inflexible for businesses with fluctuating cash flow. It is also subject to a two-year transfer restriction: SIMPLE IRA assets cannot be rolled to an IRA or another plan until two years have elapsed from the first contribution date.

For a solo operator or business with high income and no employees, the SIMPLE IRA's contribution limits are substantially lower than the Solo 401(k) and its mandatory employer contribution requirement creates unnecessary rigidity. It is rarely the best choice for purely self-employed individuals.

THE DECISION MATRIX

Net self-employment income under $150,000, no employees: → Solo 401(k). The employee deferral component allows much larger contributions at these income levels.

Net self-employment income above $200,000, no employees, prioritizing simplicity: → SEP IRA. The contribution levels converge at high incomes, and the SEP requires no annual filing or plan document establishment deadline.

Net self-employment income above $200,000, no employees, with a spouse as employee, wanting Roth option or mega backdoor Roth potential: → Solo 401(k). The Roth option and after-tax contribution potential (if the plan document supports it) add capabilities the SEP IRA cannot offer.

Business with employees:

→ SIMPLE IRA if employees are few and modest benefits suffice; traditional 401(k) with ERISA compliance if scale warrants.

TIMING AND ESTABLISHMENT RULES

SEP IRA: Can be established and funded up to the tax-filing deadline plus extensions for the prior tax year. For sole proprietors filing Schedule C, this is October 15 following the tax year. This means you can establish a SEP IRA in October 2025 and make a 2024 contribution.

Solo 401(k): The plan document must be adopted by December 31 of the year for which contributions are made. Employee deferrals must be deposited promptly after each paycheck (or by December 31 for sole proprietors with no separate payroll). Employer profit-sharing contributions can be made up to the tax-filing deadline plus extensions.

SIMPLE IRA: Must be established by October 1 of the year it will be effective, and contributions are tied to payroll schedules.

For a self-employed worker making their first retirement account decision in December, the SEP IRA's flexible establishment timeline offers an advantage. For those planning ahead, the Solo 401(k) is usually the better long-term choice.

Whatever account you choose, contributing to it consistently is the primary determinant of retirement security—the account selection is a multiplier on a decision to save that must come first.