SIMPLE IRA vs SEP vs 401(k): Small Business Retirement Plans

Once a business has employees, choosing a retirement plan stops being a personal savings decision and becomes a compensation and cost decision. The plan that lets you save the most may cost the most to cover your staff. The plan that is cheapest to run may cap your own contributions. And the plan that looks simplest on paper may lock you out of better options later. A small business retirement plan comparison has to weigh all three at once.

The three plans that cover nearly every small business are the SIMPLE IRA, the SEP IRA, and the 401(k). Each has a different contribution structure, a different set of employee obligations, and a different administrative burden. Recent changes under the SECURE 2.0 Act, especially the expanded startup credits and the rules for automatic enrollment, have shifted the balance for many owners.

This article compares the three plans on the factors that matter, works through examples for businesses of different sizes, and explains how to change plans as the business grows. It is educational, not individualized advice. Plan design should be confirmed with a third-party administrator and your CPA.

The SIMPLE IRA

The Savings Incentive Match Plan for Employees is designed for businesses with 100 or fewer employees who earned at least $5,000 in the prior year. Employees defer part of their own pay into an IRA in their name, and the employer is required to contribute in one of two ways: a dollar-for-dollar match of employee deferrals up to 3 percent of pay, or a 2 percent nonelective contribution to every eligible employee whether or not they defer. The IRS describes the plan on its SIMPLE IRA page.

The employee deferral limit for 2026 is $17,000, with an additional catch-up contribution for participants age 50 and older. Employers with 25 or fewer employees receive a slightly higher limit, and larger employers can get it by raising the match to 4 percent or the nonelective contribution to 3 percent. Contributions vest immediately. There is no annual filing, no discrimination testing, and the cost to run the plan is usually nothing beyond the custodian's account fees.

Where the SIMPLE IRA Falls Short

The owner's own savings are limited to the deferral plus the 3 percent match on their own pay. An owner earning $200,000 can put in roughly $23,000 a year, far below what a 401(k) allows. A SIMPLE IRA also cannot be combined with any other plan in the same year, so an owner cannot add a profit sharing or cash balance layer. Withdrawals in the first two years of participation carry a 25 percent penalty instead of 10 percent, and the plan must be established by October 1 to be effective for the current year. Businesses can now replace a SIMPLE IRA with a safe harbor 401(k) mid-year, which was not possible before SECURE 2.0.

The SEP IRA

A Simplified Employee Pension is an employer-funded plan with no employee deferrals. The business contributes a percentage of each eligible employee's compensation, up to 25 percent, capped at the annual defined contribution limit, which is $72,000 for 2026. Self-employed owners calculate the limit on net earnings after the deduction for the contribution itself, which works out to 20 percent of net profit. Details are on the IRS SEP page.

The SEP's appeal is flexibility and simplicity. The contribution percentage can change every year, including zero in a bad year. There is no annual filing and no testing, and the plan can be adopted and funded as late as the tax filing deadline including extensions, which makes it the plan of choice for owners who decide in March that they want a deduction for the prior year.

The Uniform Percentage Problem

The catch is that every eligible employee must receive the same percentage of pay the owner receives. If the owner contributes 25 percent for herself, she contributes 25 percent for everyone. Eligibility can be limited to employees who are at least 21, have worked for the business in three of the last five years, and earned a small minimum amount, so new hires can be excluded for a period. But once staff qualifies, the cost scales quickly. A SEP that costs an owner nothing extra with one part-time employee can cost $50,000 a year in employee contributions with five full-time staff. That is why SEPs are common for solo owners, covered in our solo 401(k) vs SEP IRA guide, and less common once a business has a real payroll.

The 401(k)

A 401(k) allows employee deferrals of $24,500 for 2026, plus a catch-up for those 50 and older and a larger catch-up in the years from 60 to 63. The employer can add a match, a profit sharing contribution, or both, up to a combined limit of $72,000 per participant for 2026, more with catch-ups. Contributions can be pre-tax or Roth. Plans can allow loans and hardship withdrawals. The IRS maintains a 401(k) resource page covering the rules.

The 401(k) is the only one of the three that lets the owner save at the full limit while employees receive a smaller percentage, and the only one that permits vesting schedules. Those two features are why most growing businesses end up with one.

Safe Harbor Designs

A traditional 401(k) must pass annual nondiscrimination tests that compare what highly compensated employees defer to what everyone else defers. If rank-and-file participation is low, the owner's deferrals get limited or refunded. A safe harbor 401(k) skips the tests by committing to a minimum employer contribution: either a 3 percent nonelective contribution to all eligible employees or a matching formula, commonly 100 percent of the first 3 percent deferred plus 50 percent of the next 2 percent. Safe harbor contributions vest immediately. For nearly every small business where the owner wants to max out, the safe harbor design is the starting point.

Profit Sharing and New Comparability

On top of deferrals and the safe harbor contribution, the employer can make a discretionary profit sharing contribution each year. A new comparability or cross-tested design divides employees into groups and allocates different percentages to each, subject to a test that looks at projected benefits at retirement rather than current contributions. Because older, higher-paid owners have fewer years to retirement, the test allows them to receive a much larger percentage than younger staff. A typical result: owners receive the full $72,000, employees receive 5 to 7 percent of pay. This is the same testing framework that makes a cash balance plan work on top of a 401(k).

Cost and Administration

A small 401(k) requires a plan document, a third-party administrator, annual Form 5500 filing, and, for plans with 100 or more participants, an audit. Expect $1,500 to $5,000 per year in administration for a plan with fewer than 25 employees, plus investment costs. Plans established after 2022 must include automatic enrollment starting at 3 percent unless the business has 10 or fewer employees or is less than three years old. Payroll integration matters: deferrals must be deposited promptly, and late deposits are one of the most common compliance failures the Department of Labor pursues.

SIMPLE IRA vs SEP vs 401(k): Side by Side

The comparison below summarizes the differences that decide most cases.

• Owner maximum: SIMPLE, roughly $17,000 plus a 3 percent match on own pay; SEP, up to $72,000 but only if the same percentage goes to every employee; 401(k), up to $72,000 with employees receiving a smaller percentage.
• Employee deferrals: SIMPLE, yes; SEP, no; 401(k), yes.
• Required employer contribution: SIMPLE, 3 percent match or 2 percent nonelective; SEP, same percentage as owner; 401(k), none for a traditional plan, 3 to 4 percent for safe harbor.
• Vesting: SIMPLE and SEP, immediate; 401(k), immediate for safe harbor and deferrals, up to a six-year schedule for match and profit sharing.
• Roth option: SIMPLE and SEP, permitted under SECURE 2.0 but not yet offered by every custodian; 401(k), widely available.
• Annual filing: SIMPLE and SEP, none; 401(k), Form 5500.
• Setup deadline: SIMPLE, October 1; SEP, tax filing deadline with extensions; 401(k), employer contributions can be made up to the filing deadline, but deferrals require the plan to exist before the pay is earned.
• Typical annual cost: SIMPLE and SEP, near zero; 401(k), $1,500 to $5,000 for a small plan before credits.

The Startup Tax Credits Changed the Math

Before SECURE 2.0, the administrative cost of a 401(k) pushed many small businesses toward a SIMPLE IRA. That calculus has changed. A business with 50 or fewer employees can now claim a credit for 100 percent of plan startup and administration costs, up to $5,000 per year for the first three years. A separate credit reimburses employer contributions of up to $1,000 per employee earning under $100,000, at 100 percent in the first two years and phasing down over the next three. Adding automatic enrollment earns an additional $500 credit per year for three years. Businesses with 51 to 100 employees get reduced versions of these credits.

For a business with eight employees, the credits can cover the entire administration cost of a safe harbor 401(k) and most of the employer contributions for the first two years. That makes the 401(k) close to free during the period when the owner is deciding whether it is worth it, and it removes the main argument for a SIMPLE IRA. Your CPA should confirm eligibility, which requires that the business not have maintained a plan covering substantially the same employees in the prior three years.

Choosing by Business Profile

The right answer follows from the owner's goals and the shape of the payroll. A few common profiles illustrate the decision.

Owner Plus One or Two Part-Time Employees

A SEP can work here if the part-time employees do not yet meet the three-of-five-years eligibility test, because the owner can contribute the full percentage with no employee cost. Once the employees qualify, the SEP gets expensive. A SIMPLE IRA is the low-cost alternative if the owner is content with a modest contribution. If the owner wants to save $50,000 or more, a safe harbor 401(k) with the startup credits is usually the better answer, and it is the answer we reach most often once a business has real payroll.

Owner Plus Five to Twenty Employees

A 401(k) almost always wins. The safe harbor contribution costs 3 to 4 percent of employee pay, which is less than the SEP's uniform percentage and comparable to the SIMPLE's match, while the owner saves three to four times what a SIMPLE allows. Adding new comparability profit sharing lets the owner reach the full limit at a manageable employee cost, and a vesting schedule on the profit sharing piece rewards retention. Owners in their late 40s and 50s who are already at the 401(k) limit can then add a cash balance plan, which requires a 401(k) rather than a SIMPLE or SEP, one more reason to choose the 401(k) early. We model these combinations as part of our retirement planning for owners.

Switching Plans as the Business Grows

Plans are not permanent. A business that starts with a SEP can adopt a 401(k) in a later year. A SIMPLE IRA can be terminated at year-end and replaced with a 401(k) the following January, or replaced mid-year with a safe harbor 401(k) under the newer rules. Employees keep their existing balances and simply stop receiving contributions to the old plan. The common path is SEP or SIMPLE while payroll is small, a safe harbor 401(k) once there are several full-time employees or the owner's income justifies the higher limit, and a cash balance plan layered on top in peak earning years. The setup deadlines above determine when each switch can happen.

For a business with employees, the retirement plan decision is really a decision about how much of the owner's savings goal the business can afford to share with staff. The SIMPLE IRA keeps costs low and savings modest. The SEP keeps administration at zero but ties employee cost directly to the owner's contribution rate. The 401(k) costs more to run, though the startup credits now offset most of it, and it is the only plan that lets owners save at the top of the range while managing what employees receive. Attend Wealth helps owners choose and coordinate plans with a third-party administrator and CPA as part of our business owner services, and our advisory services are held to a fiduciary standard. This article is educational and is not individualized advice.

Tony Colunga · Founder, Attend Wealth

Tony leads Attend Wealth, a fee-based wealth management firm in Atlanta serving professionals, families, physicians, and business owners. Advisory services are held to a fiduciary standard. More about Attend