In this article
- Who should compare these plans
- The main decision criteria
- SEP IRA overview
- SIMPLE IRA overview
- 401(k) overview
- Side-by-side comparison
- Questions to answer before choosing
- What to review with professionals
- Key takeaways
Who should compare these plans
This comparison is aimed at business owners choosing a first retirement plan, revisiting a plan they inherited, or deciding whether an existing plan still fits as the company changes. It is written for owners with either self-employment income or a small W-2 team.
The right plan usually depends less on the maximum you could contribute in an ideal year and more on how the plan interacts with your employees, your entity, and your cash flow across ordinary and slow years.
The main decision criteria
Business structure
Sole proprietorship, S corporation, partnership, and other entity types produce different definitions of eligible compensation.
Number of employees
Plans differ in how they cover eligible employees and how much employer contribution they require.
Cash flow stability
Some plans require or strongly favor consistent employer contributions each year.
Tax position
Pretax, Roth, and after-tax treatment vary across plan types and affect current versus future tax exposure.
Administrative complexity
Filing requirements, testing, and ongoing operations differ meaningfully between plan types.
Flexibility
The ability to change contribution levels, add features, or adopt loans and Roth options varies.
SEP IRA overview
A SEP IRA is an employer-funded plan that generally allows the business to contribute a percentage of eligible compensation for the owner and any eligible employees. It is straightforward to establish and typically has no annual filing requirement for the plan itself.
SEPs tend to fit owner-only businesses well. Once eligible employees exist, the required proportional contributions can meaningfully change the economics.
SIMPLE IRA overview
A SIMPLE IRA is designed for small employers and combines employee salary deferrals with a required employer contribution. Administration is lighter than a 401(k) and heavier than a SEP.
SIMPLE IRAs can suit small teams that want employee deferrals without the full complexity of a 401(k), but they include mandatory employer contributions and generally lower deferral limits than a 401(k).
401(k) overview
A 401(k) offers the most flexibility of the three: employee deferrals, potential employer contributions, Roth options, and features such as loans and profit-sharing formulas. It also carries the most administration, including annual filings and, in most cases, nondiscrimination testing.
For owner-only businesses, a solo 401(k) can pair meaningful employee-side deferrals with employer contributions. Once the company has employees, a full 401(k) generally requires a plan document, recordkeeper, and payroll coordination.
Side-by-side comparison
| Factor | SEP IRA | SIMPLE IRA | 401(k) |
|---|---|---|---|
| Employer contribution | Employer only, percentage of eligible compensation | Required employer match or nonelective contribution | Optional employer match or profit sharing |
| Employee deferrals | Not permitted | Permitted, pretax and Roth availability varies | Permitted, with pretax and Roth options |
| Employee coverage | Proportional contribution generally required for eligible employees | Available to eligible employees who meet the plan rules | Available to eligible employees, subject to plan design |
| Administration | Lightest, minimal ongoing filings | Moderate, with employer contribution obligations | Heaviest, including plan document, filings, and testing considerations |
| Flexibility | Limited feature set | Fixed structure with limited variation | Broadest feature set, including loan and Roth options where allowed |
| Common fit | Owner-only or very small teams prioritizing simplicity | Small teams wanting employee deferrals with lighter administration | Businesses seeking maximum flexibility and design control |
How SEP IRA, SIMPLE IRA, and 401(k) plans compare across the criteria most business owners care about.
Questions to answer before choosing
Information to gather
- How many eligible employees the business has today and expects over the next several years.
- How stable owner and business cash flow has been across the last three to five years.
- Whether employees expect or would benefit from a salary-deferral option.
- How much administrative capacity the business can commit to a plan.
- Whether Roth contributions, loans, or profit sharing are important to owner or team goals.
What to review with tax and retirement professionals
Financial adviser
- Which plan design most closely matches long-term retirement funding goals?
- How does the plan fit alongside other investment and savings accounts?
- How should contributions be balanced against personal reserves and business capital needs?
Tax professional
- How does entity structure affect the definition of eligible compensation?
- How do pretax and Roth contributions interact with current and projected tax brackets?
- What filings does each plan type require for the business?
Retirement plan professional
- What plan document, recordkeeper, and testing considerations apply?
- How will the plan handle future employees, turnover, and eligibility?
- What is the practical cost of running the plan on an ongoing basis?
Key takeaways
- Start from the workforce and cash-flow picture, not the maximum theoretical contribution.
- SEP IRAs favor simplicity, SIMPLE IRAs suit small teams that want deferrals, 401(k)s offer the most design flexibility.
- Employee coverage requirements, not just owner contributions, often drive the practical choice.
- Confirm current-year limits and rules with the IRS or a qualified retirement plan professional.
Sources
- Retirement Plans for Small Business — Internal Revenue Service
- Choosing a Retirement Solution for Your Small Business — U.S. Department of Labor
This article is for general educational purposes and does not provide individualized financial, investment, tax, or legal advice. Consider your full circumstances and consult the appropriate professionals before acting.
