Business 401(k) Plans vs. SIMPLE IRA, SEP, and State Programs: Cost, Limits, and Which Fits

A small business in 2026 will have four actual, realistic options for a retirement plan. They are: the 401(k) (highest limits, highest cost and administration), the SIMPLE IRA (most of the value of the 401(k) at a fraction of the costs for an organization that is less than 25 employees), the SEP IRA (employer funded only, excellent as a solo option, but it can be very costly with employee participation), and the state auto-IRA default (no fees, but the payroll work to administer this program lands on the employer, and no employer match is allowable).

In most cases for companies employing 1 to 25 workers, the SIMPLE IRA will be less expensive than the 401(k) plan. However, as business owners wish to defer contributions beyond what is allowed under SIMPLE plans or when an organization grows past 25 employees, then the 401(k) would be the best choice.

What retirement plan options does a small business have?

In addition to federal regulations, state mandates determine what you offer in terms of a 401(k), a SIMPLE IRA, a SEP IRA and the state-run auto-IRA plan which will be used as the default in California and a dozen-plus other states if no other option is provided. The real difference is who pays into the account and how costs are applied relative to each new hire. 401(k) plans are based on hiring rates (the more employees you have, the higher your administrative fees), while SIMPLE IRAs' costs remain constant. SEP plans tie your contribution rate to those of all of your employees, while auto-IRAs trade fees for your own payroll labor. These four options can be compared as follows:

What do business 401(k) plans really cost?

The 401(k) offers the most options. It has the greatest employee deferrals, in addition to profit-sharing, a Roth option, loan provisions, and various vesting schedules. It also costs the most to administer. A small-business 401(k) means a recordkeeper, a plan document, an annual Form 5500 filing, and either nondiscrimination testing or a Safe Harbor employer contribution to skip it, none of which IRS Publication 560 requires of a SIMPLE IRA.^[3] Providers charge you a fixed monthly base fee and then additional fees based on how many employees you have in your plan which will be several times what it would cost to set up and administer a SIMPLE IRA. In addition, employees usually pay asset-based fees on top.

That overhead is worth it in two situations: owners who want to defer well beyond SIMPLE limits, and businesses big enough that per-head economics dilute the fixed costs, typically after 25 employees. A specific comparison is available in SIMPLE IRA vs. 401(k), and an older high income owner may stack a cash balance plan on top if they've already reached maximums on a 401(k).

Why is a SIMPLE IRA the default under 25 employees?

A SIMPLE IRA delivers the core of the 401(k), which includes pre-tax (or Roth) payroll savings contributions from an employee of up to $17,000 with a mandatory employer contribution equal to either a dollar-for-dollar match of pay up to 3% or a flat rate of 2% for all employees. There is no Form 5500 and no nondiscrimination testing applicable under IRS SIMPLE IRA guidelines.^[1] An adoption of this type will require completion of a two-page IRS form. The obligations that remain (7-business-day deposits, the November 1 annual notice, W-2 coding) are exactly the kind of thing software automates, and these have been organized in SIMPLE IRA Rules for Employers. SECURE 2.0 provides two credits: the first reimburses 100% of a small plan's administrative costs during the first three years, with limits applied at $250 per eligible non-owner employee per year. The second credit applies separately and may reach as high as $1,000 per employee towards employer contributions.^[2]

For a five-person team of eligible non-owner employees, that credit typically covers the plan's entire administrative cost for three years, per IRAPilot analysis.

When does a SEP IRA make sense for a business?

The SEP IRA allows an employer to make a contribution of up to 25% of annual compensation with no payroll integration, determined annually as late as the tax filing deadline. For an owner-only business this is the easiest way to get a high limit plan going. The self-employed limits guide calculates contributions using owner-side contribution formulas.

There's one catch, and it is uniformity: contribute 15% for yourself and you have to pay 15% to each and every other eligible employee. A percentage "generosity" that felt free when you were solo suddenly turns into a real payroll multiplier when you've got staff.

What do state auto-IRAs mean for employers?

States such as California will automatically enroll you into one of their programs if you don't act. Roster uploads, auto-enrollment at a 5% default, and per-payroll remittance work all land on you, with no employer matching contributions allowed and IRA level limits for employee contributions. That meets the mandate requirement but does nothing else. See CalSavers employer guide for the whole picture.

How do you choose a small-business retirement plan?

Determining the most suitable small business retirement plan will depend upon three key factors: your number of employees, how much (if any) the owner wishes to defer toward their retirement and if the state's default plan is satisfactory. Determine each question in this order:

1. With zero employees, pick a SEP or solo 401(k)

   An owner-only business does not have to follow state mandates. The solo 401(k) shelters more at the same income by allowing an employee deferral in addition to the employer contribution, while the SEP can be opened and funded up until the due date of your taxes.

2. With employees, decide whether the state default is acceptable

   If you'd rather not run the state's payroll program forever, and want to be able to match, sponsor your own plan. Any qualifying plan will exempt you from the mandate.

3. Under ~25 employees, start with the SIMPLE IRA

   Lowest total cost, almost zero administration when automated, and the startup credit usually pays for it. Owners who later need bigger deferrals can convert.

4. Upgrade to a 401(k) past about 25 employees

   Around 25 to 30 employees, or when owner deferral demand outgrows SIMPLE limits, the 401(k)'s higher ceilings justify its cost. A mid-year SIMPLE-to-safe-harbor-401(k) conversion is allowed under SECURE 2.0.

The Bottom Line

In 2026 a small business has four options of plans: SIMPLE IRA, SEP IRA, 401(k), and the state auto-IRA default. For 1 to 25 employees a SIMPLE IRA usually wins on total cost, because it has no Form 5500, no testing required, and a startup credit that often covers its price for three years. Once employers wish to defer money past those allowed under SIMPLE or when their group outgrows about 25 employees, they can move to a 401(k). First count your employees.

This guide is educational and summarizes IRS rules for SIMPLE IRA plans. It is not investment, legal, or tax advice. Your plan documents and current IRS limits control. Talk to your tax advisor about your business's circumstances.