SIMPLE IRA vs 401(k)
Last updated August 2026
Short answer
Employees rarely choose between these, since the employer decides. Knowing the differences still changes how much you defer and what happens when you leave.
Contribution room
401(k): $24,500 in 2026, with an $8,000 catch-up from 50 and $11,250 at ages 60 to 63.
SIMPLE IRA: $17,000, or $18,100 in certain applicable plans, with a $4,000 catch-up from 50, or $3,850 in those plans, and $5,250 at ages 60 to 63.
The gap matters most to higher earners trying to shelter income, and barely at all to someone deferring 6% of a middling salary.
What the employer must do
In a SIMPLE IRA the contribution is mandatory: a 3% match, or 2% for all eligible employees whether they participate or not.
In a 401(k) it is discretionary. Many employers match generously and some contribute nothing at all.
A guaranteed 3% beats a hypothetical 5%, which is why the SIMPLE is not obviously worse from an employee's point of view.
Vesting and portability
SIMPLE IRA contributions vest immediately, so nothing is forfeited by leaving.
A 401(k) may apply a vesting schedule to employer money, which can mean losing part of it on an early exit.
Against that, the SIMPLE IRA carries the two-year rule, which makes early withdrawals and rollovers more expensive in the first two years than any 401(k) would be.
Try it in Walnut
Walnut connects to your brokerage and reads a SIMPLE IRA at a mainstream custodian alongside your other accounts.
Administration
A SIMPLE IRA has no nondiscrimination testing, no Form 5500 and minimal ongoing paperwork.
A 401(k) has testing, filing and fiduciary obligations, which is real cost for a business with a handful of staff.
That difference, rather than any feature employees care about, is what usually decides which plan exists.
Protections and options
401(k) assets held under ERISA generally receive strong protection from creditors, which IRA-based plans match less completely and with state variation.
Investment choice usually favours the SIMPLE IRA, since it is an IRA and not restricted to a sponsor's menu.
A good 401(k) menu with institutional pricing can beat retail IRA funds on cost, so the comparison depends on the specific plan rather than the plan type.
What changes for the employee
In a SIMPLE, everything vests immediately and the employer contribution is guaranteed, which favours shorter tenures and lower earners.
In a 401(k), the ceiling is higher and the employer contribution may be larger, but it can also be zero and may vest over years.
Neither is chosen by the employee, so the practical use of this comparison is knowing how much to defer and what happens if you leave.
Sources
The 2026 deferral and catch-up figures for both plan types are from IRS Notice 2025-67. Employer contribution requirements, the two-year rule and plan administration are in Publication 560, with plan types summarised by the Department of Labor at Types of Retirement Plans. Walnut is informational and is not an investment adviser. This guide is educational and not personalized tax advice.
FAQ
What is the main difference?
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Contribution room and cost. A 401(k) allows $24,500 of deferral in 2026 and gives the employer discretion over matching. A SIMPLE IRA allows $17,000 and requires the employer to contribute every year, but costs far less to administer.
Which is better for employees?
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Usually the 401(k), for the higher limit, larger catch-up and stronger creditor protection under ERISA. The SIMPLE IRA's guaranteed employer contribution is worth more to lower earners who were unlikely to reach either ceiling.
Which is better for a small employer?
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It depends on whether the constraint is cash or complexity. A SIMPLE IRA has no nondiscrimination testing and no Form 5500, but the employer contribution is mandatory. A 401(k) costs more to run and lets the employer skip contributions in a bad year.
What is the employer required to contribute to a SIMPLE?
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Either a dollar-for-dollar match on up to 3% of compensation for employees who defer, or 2% of compensation for every eligible employee whether they defer or not. The choice is made annually and announced in advance.
Is vesting different?
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Yes, and meaningfully. SIMPLE IRA contributions vest immediately, both yours and the employer's. A 401(k) may impose a vesting schedule on employer money, so leaving early can forfeit part of it.
What about the two-year rule?
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It applies only to the SIMPLE IRA. Within two years of your first contribution, an early withdrawal costs 25% rather than 10%, and rollovers are restricted to another SIMPLE IRA. A 401(k) has no equivalent.
Can a business have both?
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Not for the same year. An employer maintaining a SIMPLE IRA cannot also maintain another qualified plan, so switching means terminating one at a year end rather than running both.
Which has better investment options?
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Usually the SIMPLE IRA, because it is an IRA and can hold nearly anything the custodian offers. A 401(k) is limited to the menu the plan sponsor chooses, which can be excellent or poor.
Does the employee get to choose?
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No, the employer does. The practical use of the comparison is knowing how much to defer to capture the employer contribution, and knowing what happens to that money if you leave, since vesting differs sharply between the two.