401(k) or SIMPLE IRA for a small business?
Both are real retirement plans and both are used by small employers. They differ most in how much an employee can save, how much discretion the employer keeps, and how much administration comes with the plan.
A SIMPLE IRA is easier to run but caps saving lower and requires an employer contribution every year. A 401(k) allows far higher contributions and more design control, at the cost of more administration.
The comparison is often framed as simple versus complicated. That is the least useful axis, because the administration gap has narrowed while the contribution gap has not. The differences that still matter are how much can go in, and how much choice the employer keeps once the plan exists.
The contribution limits are not close
For tax year 2026, an employee may defer up to $24,500 into a 401(k). The SIMPLE IRA salary reduction limit for the same year is $17,000. Catch-up contributions widen the gap further: a 401(k) allows $8,000 for those aged 50 and over, rising to $11,250 for ages 60 to 63 under SECURE 2.0. The corresponding SIMPLE IRA figures are $4,000 and $5,250.
The total that can land in a 401(k) account from all sources — deferrals, employer contributions and forfeitures — is capped by Internal Revenue Code §415(c) at the lesser of 100% of compensation or $72,000 for 2026, or $80,000 including catch-up contributions, and up to $83,250 for those aged 60 to 63.
Every figure on this page is a 2026 figure. Contribution limits are adjusted for cost of living and change most years. Check the current year against the IRS pages linked in Sources before relying on any of them, including these.
Side by side
| 401(k) | SIMPLE IRA | |
|---|---|---|
| Employee deferral limit | $24,500 | $17,000 |
| Catch-up, age 50 and over | $8,000 | $4,000 |
| Catch-up, ages 60 to 63 | $11,250 | $5,250 |
| Employer contribution | Discretionary, unless the plan uses a safe harbor design or is subject to another rule requiring one. | Required every year: either a dollar-for-dollar match up to 3% of compensation, or a 2% non-elective contribution for every eligible employee. |
| Annual nondiscrimination testing | Required for a traditional design (ADP and ACP). A safe harbor design removes it. | None. The required employer contribution takes the place of testing. |
| Vesting of employer money | May use a vesting schedule, so unvested amounts return to the plan when someone leaves early. | Immediate. Every employer dollar belongs to the employee straight away. |
| Loans | Permitted if the plan document allows them. | Not available. |
| Annual Form 5500 | Required. In a pooled employer plan the provider files one return for all participating employers. | Generally not required. |
| Design flexibility | Eligibility, entry dates, match formula, vesting and automatic enrolment are all choices. | Deliberately few choices, which is the point of it. |
Figures are tax year 2026 and are cost-of-living adjusted. The employer-contribution row is the one that decides this question for most businesses.
The required employer contribution is the real trade
A SIMPLE IRA removes annual testing, and it removes it by requiring the employer to contribute every year — either matching each participating employee dollar-for-dollar up to 3% of compensation, or contributing 2% of compensation for every eligible employee whether or not they participate. That is a genuine simplification, and it is also a standing obligation that does not flex with a bad year.
A traditional 401(k) leaves employer contributions discretionary but brings the ADP and ACP tests, which check that deferrals by highly compensated employees do not run too far ahead of everyone else. A safe harbor 401(k) sits between the two: it removes those tests, and it does so the same way a SIMPLE IRA does, by committing the employer to a contribution.
So the honest comparison is often safe harbor 401(k) versus SIMPLE IRA, not 401(k) versus SIMPLE IRA. Both commit the employer to contribute. The 401(k) version lets employees save substantially more, permits a vesting schedule so early leavers do not keep unvested employer money, and allows loans. It carries a Form 5500 and more administration in exchange.
When each one tends to fit
A SIMPLE IRA tends to suit a very small employer with stable headcount, no appetite for plan design decisions, and no owner or senior employee trying to save near the higher limits. Its obligations are predictable and its administration is genuinely light.
A 401(k) tends to suit an employer who wants employees to be able to save meaningfully more, wants vesting to work as a retention tool, expects headcount to change, or wants the option of automatic enrolment. It also suits any business where someone wants to contribute above the SIMPLE limits, which is a common and entirely ordinary reason to choose one.
The administrative objection to a 401(k) is the part that has changed most. Where a plan's recurring work is automated rather than performed by hand each pay period, the gap between the two on employer effort narrows considerably — which moves the decision back onto contribution limits and design, where it belongs.
Switching between them
Moving from a SIMPLE IRA to a 401(k) is not a same-day change. SIMPLE IRA plans run on a calendar year and have their own notice requirements, and an employer generally cannot maintain a SIMPLE IRA and another qualified plan covering the same employees for the same year. Plan the transition around plan years rather than around a start date, and confirm the sequence with your advisor before terminating anything.
One more thing worth knowing before switching: the federal startup credit under §45E is not available where the employer maintained a qualified plan covering substantially the same employees in the three tax years before the first credit year. Whether a prior SIMPLE IRA triggers that is a question for a qualified tax advisor, and it is worth asking before you assume a credit.
Common questions
Is a 401(k) or a SIMPLE IRA better for a small business?
Neither is better in general. A SIMPLE IRA is lighter to run but caps employee saving lower and requires an employer contribution every year. A 401(k) allows far higher contributions, permits vesting and loans, and offers real design control, in exchange for more administration and an annual Form 5500.
How much can an employee contribute to each in 2026?
For tax year 2026 the 401(k) elective deferral limit is $24,500 and the SIMPLE IRA salary reduction limit is $17,000. Catch-up contributions are $8,000 and $4,000 respectively for those aged 50 and over, rising to $11,250 and $5,250 for ages 60 to 63. These limits are cost-of-living adjusted and change most years.
Does a SIMPLE IRA require the employer to contribute?
Yes, every year. The employer either matches each employee's salary reduction contributions dollar-for-dollar up to 3% of compensation, or makes a non-elective contribution of 2% of compensation for every eligible employee regardless of whether they contribute.
Can a 401(k) avoid annual nondiscrimination testing?
Yes, with a safe harbor design. A safe harbor 401(k) removes the annual ADP and ACP tests in exchange for a committed employer contribution — the same trade a SIMPLE IRA makes, but with the higher 401(k) contribution limits, an available vesting schedule, and the option of loans.
Can an employer have both a SIMPLE IRA and a 401(k)?
Generally not for the same employees in the same year. A switch has to be planned around plan years and notice requirements. It is also worth checking with a tax advisor whether a prior plan affects eligibility for the §45E startup credit, which is unavailable where a qualified plan covered substantially the same employees in the prior three tax years.
Sources
- Internal Revenue Service, Retirement Topics — 401(k) and Profit-Sharing Plan Contribution Limits — the 2026 elective deferral limit, the age-50 and ages 60-63 catch-up amounts, and the §415(c) annual additions limit
- Internal Revenue Service, Retirement Topics — SIMPLE IRA Contribution Limits — the 2026 SIMPLE IRA salary reduction limit, its catch-up amounts, and the 3% match or 2% non-elective employer requirement
- Internal Revenue Service, 401(k) Plan Overview — annual ADP and ACP testing for traditional 401(k) plans, and that safe harbor designs remove it
- Internal Revenue Service, Retirement Plans Startup Costs Tax Credit — that the §45E credit is unavailable where a qualified plan covered substantially the same employees in the prior three tax years
- U.S. Department of Labor, Form 5500 Series — the annual return requirement and its filing deadline
aipep401k.com is a pooled employer plan for small business 401(k) plans, operated by ThinkNirvana Foundation — plan administration handled by automation rather than assembled by hand.
Related: which employees a 401(k) has to cover, what drives the cost of setting one up. To see what a plan design would look like for your own headcount, the plan design tool is free and needs no sign-up.