SEP IRA vs Solo 401(k) vs SIMPLE IRA

Three plan types dominate conversations about small business retirement savings: the SEP IRA, the solo 401(k), and the SIMPLE IRA. All three offer tax-deferred growth and generally deductible contributions, but they differ in how contributions work, how employees are treated, and how much they cost to run.

SEP IRA

A Simplified Employee Pension plan is funded by employer contributions only. The contribution for each eligible employee, including the owner, is generally the same percentage of compensation, up to a dollar limit. There is no employee deferral component in the usual SEP.

Advantages include easy setup, minimal administration, and flexibility to vary the contribution each year or skip a year. Disadvantages include the requirement to contribute the same percentage for eligible employees, no standard Roth option in most cases, and lower total capacity at moderate incomes compared with a solo 401(k), because there is no employee deferral piece.

Solo 401(k)

The solo 401(k) allows both employee deferrals and employer contributions, which often produces a higher combined contribution at moderate income levels. It may offer a Roth deferral option and loans, depending on the plan document. It generally suits owners with no employees other than a spouse. It has slightly more administrative work, and at higher asset levels an annual filing may be required. See Solo 401(k) Plans for Owner-Operators.

SIMPLE IRA

A Savings Incentive Match Plan for Employees is designed for small employers and includes employee deferrals plus a required employer contribution, either a match or a fixed nonelective contribution. Employee deferral limits are lower than for a 401(k), and the plan generally must be established by a set date in the year. It is inexpensive to run and can suit businesses with several employees who want a straightforward plan. It is often less attractive for owners who want high contributions.

Side-by-Side Snapshot

Thinking About Contribution Capacity

The best way to compare capacity is to model your own income. For an owner with a given compensation figure, calculate the maximum under each plan, then compare it to the amount you actually intend to contribute. If you plan to save less than the SEP limit, the higher capacity of a 401(k) may not matter. If you plan to maximize contributions, capacity becomes a deciding factor.

Employees and Cost

If you have or expect to hire employees, the cost of covering them is central. A SEP requires the same percentage contribution for eligible employees as you make for yourself. A SIMPLE requires a match or nonelective contribution but limits employee deferrals. A solo 401(k) is generally not available once you have eligible common-law employees, at which point a traditional 401(k) may be considered. See Retirement Plans When Your Business Has Employees.

Timing and Flexibility

A SEP can often be established and funded up to the tax filing deadline including extensions, which makes it a useful year-end catch-up tool. A solo 401(k) has additional flexibility but may require earlier action for employee deferrals. A SIMPLE has a fixed establishment date. Recent legislation adjusted some of these timelines, so confirm current dates.

Moving Between Plans

Owners often start with a SEP and move to a solo 401(k) or a defined benefit plan as income grows. Moves between plan types are common and generally straightforward, but plan documents and rollover rules should be followed. Check for restrictions, such as waiting periods after a SIMPLE IRA is established.

Questions to Ask

1. Do I have or expect employees?
2. What is my target contribution?
3. Do I want Roth contributions?
4. How much administration am I willing to take on?

For plans with higher capacity, see Defined Benefit Plans for Business Owners. For the general overview, see Retirement Plans for Business Owners: An Overview.

A Hypothetical Choice Between Plans

Consider three owners. The first is a consultant with no staff who wants to save a moderate amount each year and dislikes paperwork. A SEP IRA may fit. The second is an S corporation owner with no staff who wants to defer a larger amount and is interested in Roth contributions. A solo 401(k) may fit better. The third runs a small shop with a handful of employees and wants a simple way to offer a plan without testing. A SIMPLE IRA may deserve a look. These are hypothetical profiles and the right answer for any real business depends on the facts.

Revisit Annually

Plan fit changes. A consultant who hires staff, an owner whose income jumps, or an owner nearing retirement may want to move to a different design. Set a reminder to review the plan each fall, before year-end deadlines.

Educational purposes only. This page is general education and is not tax, legal, or accounting advice. Tax laws change and outcomes depend on individual facts, so consult a qualified professional before acting. No result is guaranteed.